Compositions for booster vaccination against dengue

Abstract

The present invention is directed to a method of booster vaccination and to a vaccine composition for use in such a method, for inducing in a human subject a neutralizing antibody response, wherein said subject has previously received a primary vaccination against each of serotypes 1 to 4 of dengue virus and was dengue naïve before said primary vaccination, said composition comprising a dengue antigen of at least one of serotypes 1 to 4 or a nucleic acid construct capable of expressing said antigens in the subject, wherein said booster vaccination results in a 2-fold increase in the neutralizing antibody titre against each of serotypes 1 to 4. The invention is also directed to a method of inducing in a human subject a neutralizing antibody response comprising the administration of a vaccine composition, or to a vaccine composition for use in such a method, said composition comprising a dengue antigen of each of serotypes 1 to 4, or a nucleic acid construct capable of expressing in said subject a dengue antigen of each of serotypes 1 to 4; wherein said composition is administered as a primary vaccination, followed by a booster vaccination, and wherein the human subject is initially dengue naïve.

Claims

1. A method of booster vaccination for inducing in a human subject a neutralizing antibody response against dengue virus, said method comprising administering to said human subject a composition comprising a dengue antigen of each of serotypes 1 to 4 wherein each of said dengue antigens is independently selected from the list consisting of: (a) a live attenuated dengue virus and (b) a live attenuated chimeric dengue virus, wherein said subject has previously received a primary vaccination course against each of serotypes 1 to 4 of dengue virus, and said subject was dengue naïve before said primary vaccination course, wherein said booster vaccination is administered at least one year after the end of the primary vaccination course and results in at least a 2-fold increase in the neutralizing antibody titre against each of serotypes 1 to 4, wherein said dengue antigens of serotypes 1 to 4 comprise nucleic acid sequences having at least 90% identity to SEQ ID NOs: 1, 2, 3 and 4 respectively, and wherein the amino acid at position 226 of the Envelope (E) protein of the dengue antigen of serotype 2 is threonine, the amino acid at position 228 of the Envelope (E) protein of the dengue antigen of serotype 2 is glycine, and the amino acid at position 251 of the Envelope (E) protein of the dengue antigen of serotype 2 is valine.

2. The method according to claim 1, wherein the booster vaccination is administered at least two years after the end of the primary vaccination course.

3. The method according to claim 1, wherein said primary vaccination course is administered in one, two or three doses.

4. The method according to claim 1, wherein the subject has, before booster administration, a neutralizing antibody titer as measured using a dengue Plaque Reduction Neutralization Test (PRNT.sub.50) test against each of serotypes 1 to 4 of at least 10 and less than 150.

5. The method according to claim 1, wherein said 2-fold increase in the neutralizing antibody titre against each of serotypes 1 to 4 is measured between 20 and 60 days after said booster vaccination.

6. The method according to claim 1, wherein said neutralizing antibody titre is measured using a dengue Plaque Reduction Neutralization Test (PRNT.sub.50) test.

7. The method according to claim 1, wherein said vaccine composition administered for booster vaccination is identical to the vaccine composition previously administered during the primary vaccination course.

8. A method of inducing in a human subject a neutralizing antibody response against dengue virus, said method comprising administering to said human subject a composition comprising a dengue antigen of each of serotypes 1 to 4, wherein said dengue antigens of serotypes 1 to 4 are each independently selected from the group consisting of a live attenuated dengue virus and a live attenuated chimeric dengue virus, wherein said dengue antigens of serotypes 1 to 4 comprise nucleic acid sequences having at least 90% identity to SEQ ID NOs: 1, 2, 3 and 4 respectively; wherein the amino acid at position 226 of the Envelope (E) protein of the dengue antigen of serotype 2 is threonine, the amino acid at position 228 of the Envelope (E) protein of the dengue antigen of serotype 2 is glycine, and the amino acid at position 251 of the Envelope (E) protein of the dengue antigen of serotype 2 is valine, wherein said composition is administered as: (a) a primary vaccination, followed at least 1 year after the end of the primary vaccination course by (b) a booster vaccination, and wherein the human subject is initially dengue naïve.

9. The method according to claim 8, wherein the booster immunization is administered at least two years after the end of the primary vaccination course.

10. The method according to claim 8, wherein said primary vaccination course is administered in one, two or three doses.

11. The method according to claim 8, wherein said subject is at least around 9 years of age.

12. The method according to claim 8, wherein said booster vaccination results in at least a 2-fold increase in the neutralizing antibody titre against each of serotypes 1 to 4, when compared with the neutralizing antibody titres induced after the primary vaccination.

13. The method according to claim 12, wherein said 2-fold increase in the neutralizing antibody titre against each of serotypes 1 to 4 is measured between 20 and 60 days after said booster vaccination.

14. The method according to claim 12, wherein said neutralizing antibody titre is measured using a dengue Plaque Reduction Neutralization Test (PRNT.sub.50) test.

15. The method according to claim 1, wherein said human subject is protected against dengue disease.

16. The according to claim 1, wherein said subject is aged between 9 months and 60 years old.

17. The method according to claim 8, wherein said primary vaccination course consists in administration of 3 vaccine doses, wherein the second dose is administered about 6 months after the first dose and the third dose is administered about 6 months after the second dose.

18. The method according to claim 1, wherein the booster immunization is administered less than 20 years after the end of the primary vaccination course.

19. The method according to claim 1, wherein the human subject is resident in a dengue endemic area.

20. The method according to claim 1, wherein said live attenuated chimeric dengue virus comprises a genome from a first flavivirus in which the prM-E sequence has been replaced with a prM-E sequence of a dengue virus.

21. A method of booster vaccination for inducing in a human subject a neutralizing antibody response against dengue virus, said method comprising administering to said human subject a composition comprising a dengue antigen of each of serotypes 1 to 4 wherein each of said dengue antigens is independently selected from the list consisting of: (a) a live attenuated dengue virus and (b) a live attenuated chimeric dengue virus, wherein said subject has previously received a primary vaccination course against each of serotypes 1 to 4 of dengue virus, and said subject was dengue naïve before said primary vaccination course, wherein said booster vaccination is administered at least one year after the end of the primary vaccination course and results in at least a 2-fold increase in the neutralizing antibody titre against each of serotypes 1 to 4; wherein said dengue antigens of serotypes 1, 3 and 4 comprise nucleic acid sequences having at least 90% identity to SEQ ID NOs: 1, 3 and 4 respectively, wherein said dengue antigen of serotype 2 comprises a nucleic acid sequence having at least 95% identity to SEQ ID No: 2; and wherein Envelope (E) protein encoded by the nucleic acid sequence of the dengue antigen of serotype 2 comprises a threonine residue at the position within the protein which correspondence to position 226 of SEQ ID NO: 2, a glycine residue at the position within the protein which corresponds to position 228 of SEQ ID NO: 2 and a valine residue at the position within the protein which corresponds to position 251 of SEQ ID NO: 2.

22. A method of inducing in a human subject a neutralizing antibody response against dengue virus, said method comprising administering to said human subject a composition comprising a dengue antigen of each of serotypes 1 to 4, wherein said dengue antigens of serotypes 1 to 4 are each independently selected from the group consisting of a live attenuated dengue virus and a live attenuated chimeric dengue virus, wherein said dengue antigens of serotypes 1, 3 and 4 comprise nucleic acid sequences having at least 90% identity to SEQ ID NOs: 1, 3 and 4 respectively, wherein said dengue antigen of serotype 2 comprises a nucleic acid sequence having at least 95% identity to SEQ ID No: 2; and wherein Envelope (E) protein encoded by the nucleic acid sequence of the dengue antigen of serotype 2 comprises a threonine residue at the position within the protein which correspondence to position 226 of SEQ ID NO: 2, a glycine residue at the position within the protein which corresponds to position 228 of SEQ ID NO: 2 and a valine residue at the position within the protein which corresponds to position 251 of SEQ ID NO: 2, wherein said composition is administered as: (a) a primary vaccination, followed at least 1 year after the end of the primary vaccination course by (b) a booster vaccination, and wherein the human subject is initially dengue naïve.

Description

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(1) The present inventors have demonstrated that the administration of a booster dengue vaccine unexpectedly induces an increase of the neutralizing antibody titres in subjects who were dengue naïve before the primary vaccination, which is proportionally greater than the increase in subjects who were dengue immune before said primary vaccination. Whereas the immune response to primary vaccination against dengue virus is more effective in human subjects who are dengue immune prior to the primary vaccination, the inventors have now demonstrated that the degree of modulation of the immune response to a booster vaccination is modest in this population, with respect to human subjects who have not been infected (i.e. who were dengue naïve prior to the primary vaccination) for which the degree of modulation is unexpectedly high.

(2) According to a first aspect, the present invention thus relates to a method of booster vaccination and to a vaccine composition for use in such a method for inducing in a human subject an immune response, wherein said subject has previously received a primary vaccination against each of serotypes 1 to 4 of dengue virus and was dengue naïve before said primary vaccination, preferably was flavivirus naïve before said primary vaccination. Such a subject has preferably not previously been naturally infected by a dengue virus, and preferably not previously been naturally infected by a flavivirus.

(3) The method of booster vaccination according to the invention comprises the step of administering the vaccine composition to the human subject.

(4) The immune response induced by the vaccine composition of the invention or by the method of the invention is preferably a humoral response, especially a response comprising the production of neutralizing antibodies against dengue virus, i.e. a neutralizing antibody response. According to a preferred embodiment, the neutralizing antibodies are directed against each of serotypes 1 to 4 of dengue virus.

(5) In a preferred embodiment, the method of booster vaccination and the vaccine composition for use as a booster according to this aspect of the invention induces at least a two-fold increase in the titers of neutralizing antibodies in the subjects receiving the booster, for at least one of the dengue serotypes, preferably for at least two, most preferably for at least 3, and even more preferably for each of serotypes 1 to 4, by comparison to the titers of neutralizing antibodies before the booster administration. Preferably the comparison is made between the levels measured a few days before the booster administration and around 28 days or one month after its administration. Alternatively, the level after the booster administration is measured around one or two months after said administration, preferably between around 20 days and 60 days after said booster vaccination, especially around 28 days after said booster vaccination. The titre of neutralizing antibodies is advantageously measured by the PRNT.sub.50 test. The neutralizing antibody titre is thus advantageously assimilated to the PRNT.sub.50 titre in the following.

(6) In another preferred embodiment, the vaccine composition for use as a booster and the corresponding method according to this aspect of the invention induces at least a four-fold increase in the titres of neutralizing antibodies in a human subject receiving the booster, for at least one of the dengue serotypes, preferably for at least two dengue serotypes, or more, preferably for at least serotype 4, or for serotypes 3 and 4.

(7) The present inventors have also demonstrated that such a booster vaccination unexpectedly induces a seroconversion rate after the booster, for each serotype of the dengue virus, which is greatly increased in subjects who were dengue non-immune before the primary vaccination, with respect to the seroconversion rate in subjects who were dengue immune before the primary vaccination, by a factor of at least 2 to 5 (see table 8 of the experimental section). According to a preferred embodiment, the seroconversion rate after the booster vaccination according to the invention, in human subjects who have previously received a primary vaccination against each of serotypes 1 to 4 of dengue virus but who were dengue naïve before said primary vaccination, is at least about 30% for each serotype, preferably at least 35% for serotype 1 or at least 35% for serotype 2, at least 45% for serotype 3. The seroconversion rate after a booster vaccination is preferably estimated on a population of at least 10 different human subjects receiving the booster vaccination, preferably on a population of at least 50 subjects, even more preferably on a population of at least 100 subjects.

(8) The inventors have demonstrated that, not only is the seroconversion rate of the booster vaccination increased in subjects who were dengue non-immune before the primary vaccination, with respect to the seroconversion rate in subjects who were dengue immune before the primary vaccination, but also that the relative rate of decline in the titre of neutralizing antibodies is lower in subjects who were dengue non-immune before the primary vaccination, with respect to the relative rate of decline in subjects who were dengue immune before the primary vaccination. Indeed, as illustrated in table 15, one year after the booster vaccination, the additive effect of the booster dose, on the titre of neutralizing antibodies, is still present in baseline naïve subjects and has disappeared in baseline immune subjects. The additive effect of the booster dose is thus more durable in baseline naïve subjects than in baseline immune subjects. More specifically, one year after the booster vaccination or more, the titre of neutralizing antibodies in the subjects receiving the booster is preferably still increased with respect to the level before the booster vaccination, preferably by a factor of at least 1.2, or at least 1.3 or more, in dengue-naïve subjects before the primary vaccination. Such an increased titre over at least one year after the booster vaccination is for at least one serotype, preferably at least two or three, preferably for the 4 serotypes.

(9) The vaccine composition for use in a booster vaccination according to the invention is for use in a human subject who has previously been vaccinated against dengue disease, and was flavivirus naïve before said primary vaccination. Preferably, the subject has not been naturally infected by a flavivirus, i.e. has not been infected by a flavivirus before the booster vaccination. Preferably the subject has not been previously naturally infected by a yellow fever virus, a dengue virus, irrespective of the serotype, or a Zika virus. Even more preferably, the subject to receive the booster vaccination has not been naturally infected by a dengue virus or a Zika virus. Most preferably, the human subject has not previously been naturally infected by a dengue virus, irrespective of the serotype. Before the primary vaccination, a human subject was thus dengue naïve, preferably dengue naïve and Zika naïve and even more preferably yellow fever naïve, dengue naïve and Zika naïve.

(10) A preferred human subject is thus a subject who has, before the administration of the booster, a PRNT.sub.50 titre against each of serotypes 1 to 4 of at least 10, (i.e. the subject is dengue immune due to the primary vaccination), but who has a PRNT.sub.50 titre of less than 150, preferably less than 120, or preferably less than 100, preferably less than 80, preferably less than 60, preferably less than 40 or even less than 30, indicating that the subject has not been naturally infected by a dengue virus and was dengue naïve prior to the primary vaccination.

(11) The absence of a prior natural infection by a dengue virus can also been confirmed by the absence of detection of antibodies against dengue virus antigens which may not be present in a dengue vaccine, for example antibodies against dengue non-structural protein 1 (NS1) antigen, which is absent from at least Dengvaxia®. Various tests for detecting antibodies against dengue NS1 protein are well known in the art.

(12) A subject likely to be treated by the method of the invention, i.e. a subject who has received a primary vaccination but who has not been naturally infected, or a subject who was dengue naïve before the primary vaccination, is also characterized by the type or quality of neutralizing antibodies present in the subject. Such a subject is for example characterized as exhibiting an essentially homotypic neutralizing antibody response against only one of the 4 serotypes, and a mixed homotypic and heterotypic neutralizing antibody response against the 3 other serotypes. Preferably, the subject to be treated according to this 1.sup.st aspect exhibits an essentially homotypic neutralizing antibody response against dengue virus serotype 4, and a mixed homotypic and heterotypic neutralizing antibody response against dengue virus serotypes 1-3.

(13) The previous dengue infection according to the present invention may be virologically-confirmed dengue disease.

(14) The vaccine composition according to the invention comprises a dengue antigen of at least one of serotypes 1 to 4 or a nucleic acid construct capable of expressing said antigen(s) in the subject. According to a preferred embodiment, the vaccine composition comprises: (i) a dengue antigen of at least one of serotypes 1 to 4, wherein said dengue antigen(s) of at least one of serotypes 1 to 4 is (are each independently) selected from the group consisting of: (a) a live attenuated dengue virus; and (b) a live attenuated chimeric dengue virus; or (ii) a nucleic acid construct(s) which is (are) able to express in said human subject a dengue antigen of at least one of serotypes 1 to 4, wherein said dengue antigen(s) is (are) dengue VLPs.

(15) According to a preferred embodiment, the vaccine composition comprises: (i) a dengue antigen of each of serotypes 1 to 4, wherein said dengue antigens of each of serotypes 1 to 4 are each independently selected from the group consisting of: (a) a live attenuated dengue virus; and (b) a live attenuated chimeric dengue virus; or (iii) a nucleic acid construct or constructs which is (are) able to express in said human subject a dengue antigen of each of serotypes 1 to 4, wherein said dengue antigens are dengue VLPs.

(16) According to another embodiment, the vaccine composition comprises a dengue antigen, or nucleic acid able to express a dengue antigen, of least 2 serotypes, preferably at least 3 serotypes, for example serotypes 1, 2 and 4.

(17) Preferably a vaccine composition according to the present invention comprises a dengue antigen of each of serotypes 1 to 4 which are each independently selected from the group consisting of: (a) a live attenuated dengue virus and (b) a live attenuated chimeric virus.

(18) Preferably a vaccine composition according to the present invention comprises a dengue antigen of at least one, two, three or each of serotypes 1 to 4, wherein at least one of said dengue antigens is a live attenuated chimeric virus, preferably a live attenuated chimeric dengue virus, even more preferably a live attenuated chimeric dengue/dengue virus or a live attenuated chimeric YF/dengue virus. For example, the dengue antigen of serotype 2 is a live attenuated chimeric dengue/dengue virus. For example, a vaccine composition according to the present invention may be any of the tetravalent mixtures of dengue antigens of each of serotypes 1 to 4 (referred to as TV001, TV002, TV003 and TV004) which are disclosed in Durbin et al., Journal of Infectious Diseases (2013), 207, 957-965. Preferably, a vaccine composition according to this embodiment of the invention is TV003.

(19) Preferably a vaccine composition according to the present invention comprises a dengue antigen of at least one, two, three or each of serotypes 1 to 4, wherein said dengue antigens are each a live attenuated chimeric dengue virus. For example, a vaccine composition of the present invention may comprise a dengue antigen of each of serotypes 1 to 4, wherein said dengue antigens of serotypes 1, 3 and 4 are each a live attenuated chimeric dengue/dengue virus and said dengue antigen of serotype 2 is a live attenuated dengue virus. For example, a vaccine composition according to the present invention may be the tetravalent mixture of dengue antigens of each of serotypes 1 to 4 (referred to as DENVax) which is disclosed in Huang et al., PLoS Negl Trop Dis 7(5): e2243 (2013). Alternatively, a vaccine composition of the present invention may comprise a dengue antigen of each of serotypes 1 to 4, wherein said dengue antigens of serotypes 1, 3 and 4 are each a live attenuated chimeric YF/dengue virus and said dengue antigen of serotype 2 is a live attenuated dengue virus.

(20) Preferably a vaccine composition according to the present invention comprises a dengue antigen of each of serotypes 1 to 4, wherein each of said dengue antigens is a live attenuated chimeric dengue virus, preferably a chimeric YF/dengue virus, more preferably a chimeric YF/dengue virus which comprises an attenuated YF genomic backbone whose prM-E sequence has been substituted with the prM-E sequence of dengue virus.

(21) Preferably, a live attenuated chimeric dengue virus of the present invention comprises one or more proteins from a dengue virus and one or more proteins from a different flavivirus. Preferably, the different flavivirus is a yellow fever virus (i.e. a chimeric YF/dengue virus). Preferably a live attenuated chimeric dengue virus according to the present invention comprises an attenuated yellow fever virus genome whose prM-E sequence has been substituted with the prM-E sequence of a dengue virus. Alternatively, a live attenuated chimeric dengue virus of the present invention comprises one or more proteins from a first dengue virus and one or more proteins from a second dengue virus (i.e. a chimeric dengue/dengue virus). Preferably said first dengue virus and said second dengue virus are of different serotypes. Where said first dengue virus and said second dengue virus are of the same serotype, said first and second dengue viruses are different strains.

(22) A preferred example of a dengue antigen of serotype 1 for use in the present invention is a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 1. Another preferred example of a dengue antigen of serotype 1 for use in the present invention is a live attenuated dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 6. Preferably a nucleotide sequence that has less than 100% identity to SEQ ID NO: 6 does not comprise mutations at the positions within said nucleic acid sequence which correspond to positions 1323, 1541, 1543, 1545, 1567, 1608, 2363, 2695, 2782, 5063, 5962, 6048, 6806, 7330, 7947 and 9445 of SEQ ID NO: 6.

(23) A preferred example of a dengue antigen of serotype 2 for use in the present invention is a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 2. Another preferred example of a dengue antigen of serotype 2 for use in the present invention is a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 5. Another preferred example of a dengue antigen of serotype 2 for use in the present invention is a live attenuated dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 7. Preferably a nucleotide sequence that has less than 100% identity to SEQ ID NO: 7 does not comprise mutations at the positions within said nucleic acid sequence which correspond to positions 736, 1619, 4723, 5062, 9191, 10063, 10507, 57, 524, 2055, 2579, 4018, 5547, 6599 and 8571 of SEQ ID NO: 7.

(24) Advantageously, a dengue antigen of serotype 2 for use in the present invention (whether said dengue antigen is, for example, a live attenuated dengue virus, a chimeric dengue virus or a VLP) comprises a Thr residue at position E-226 and/or a Val residue at position E-251. More advantageously, said dengue antigen of serotype 2 comprises a Thr residue at position E-226, a Gly residue at position E-228 and a Val residue at position E-251 In this context, E-226 designates position 226 of the Envelope (E) protein etc. The identity of an amino acid residue at a particular position can easily be determined by protein alignment, for example by alignment with the protein sequence of the E protein from CYD2, which may be easily derived from SEQ ID NO: 2.

(25) A preferred example of a dengue antigen of serotype 3 for use in the present invention is a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 3.

(26) A preferred example of a dengue antigen of serotype 4 for use in the present invention is a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 4.

(27) In order to form a tetravalent dosage form of a booster composition for use according to the present invention (i.e. one containing a dengue antigen of each of serotypes 1 to 4), the preferred examples of dengue antigens of serotypes 1, 2, 3 and 4 disclosed in the preceding four paragraphs may be combined in any combination possible. Alternatively, a booster composition for use according to the present invention may be administered to a subject as bivalent dosage forms, or tetravalent dosage forms, wherein the preferred examples of dengue antigens of serotypes 1, 2, 3 and 4 disclosed in the preceding four paragraphs may be combined in any pair of bivalent or tetravalent combinations that are possible. Thus, in particularly preferred combinations of dengue antigens of serotypes 1, 2, 3 and 4, the dengue antigens of serotypes 3 and 4 are respectively a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 3 and a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 4. In such particularly preferred combinations, the dengue antigens of serotypes 1 and 2 may respectively be: (i) a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 1 and a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 2; or (ii) a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 1 and a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 5; or (iii) a live attenuated chimeric YF/dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 1 and a live attenuated dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 7 (preferably a nucleotide sequence that has less than 100% identity to SEQ ID NO: 7 does not comprise mutations at the positions within said nucleic acid sequence which correspond to positions 736, 1619, 4723, 5062, 9191, 10063, 10507, 57, 524, 2055, 2579, 4018, 5547, 6599 and 8571 of SEQ ID NO: 7); or (iv) a live attenuated dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 6 (preferably a nucleotide sequence that has less than 100% identity to SEQ ID NO: 6 does not comprise mutations at the positions within said nucleic acid sequence which correspond to positions 1323, 1541, 1543, 1545, 1567, 1608, 2363, 2695, 2782, 5063, 5962, 6048, 6806, 7330, 7947 and 9445 of SEQ ID NO: 6 and a live attenuated dengue virus which comprises a nucleotide sequence having at least 90%, at least 95%, at least 98% or 100% sequence identity to SEQ ID NO: 7 (preferably a nucleotide sequence that has less than 100% identity to SEQ ID NO: 7 does not comprise mutations at the positions within said nucleic acid sequence which correspond to positions 736, 1619, 4723, 5062, 9191, 10063, 10507, 57, 524, 2055, 2579, 4018, 5547, 6599 and 8571 of SEQ ID NO: 7).

(28) The vaccine composition for use according to this 1.sup.st aspect of the invention, as a booster vaccination, may advantageously be identical to the vaccine composition previously administered during the primary vaccination course. Alternatively, according to a different embodiment, the vaccine composition for use as a booster vaccination, may be different from the vaccine composition previously administered during the primary vaccination course. It may inter alia comprise antigen of only one serotype whereas the primary vaccination comprises antigens of each of serotypes 1-4; it may also comprise different excipients, different dosages. It may also be an entirely different vaccine composition; for example the primary vaccination is based on live attenuated chimeric dengue/dengue viruses, and the booster vaccination is based on live attenuated chimeric YF/dengue viruses.

(29) According to a second aspect, the present invention is directed to a method of inducing in a human subject a neutralizing antibody response against dengue virus, and to a vaccine composition for use in such a method, said composition comprising a dengue antigen of each of serotypes 1 to 4, or a nucleic acid construct capable of expressing in said subject a dengue antigen of each of serotypes 1 to 4;

(30) wherein said composition is administered as:

(31) (a) a primary vaccination, followed by (b) a booster vaccination,
and wherein the human subject is initially dengue naïve.

(32) The method of inducing in a human subject a neutralizing antibody response against dengue virus according to this second aspect comprises the steps of (a) administering a vaccine composition as a primary vaccination, and of (b) subsequently administering a vaccine composition (which may be the same or different as the primary vaccination composition) as a booster vaccination.

(33) Preferably, the dengue antigens of serotypes 1 to 4 are each independently selected from the group consisting of a live attenuated dengue virus and a live attenuated chimeric dengue virus.

(34) Alternatively, the vaccine composition for use according this second aspect of the invention comprises one or more nucleic acid constructs capable of expressing dengue VLPs of each of serotypes 1 to 4.

(35) All the preferred types and combinations of antigens of serotypes 1 to 4 detailed with regard to the first aspect of the invention are entirely applicable to this second aspect of the invention; inter alia, according to a preferred embodiment, the dengue antigens of serotypes 1 to 4 are each independently live attenuated chimeric dengue viruses, especially they are each independently selected from the group consisting of live attenuated chimeric dengue/dengue and YF/dengue viruses. According to preferred embodiments, the dengue antigens of serotypes 1 to 4 are all live attenuated chimeric dengue/dengue viruses, or they are all live attenuated chimeric YF/dengue viruses.

(36) Preferably, said immune response comprising the production of neutralizing antibodies against dengue virus, or said neutralizing antibody response, according to the first and second aspects of the invention results in a certain level of vaccine efficacy, preferably it is protecting the human subject against dengue disease caused by a dengue virus of at least one of serotype 1, 2, 3 and 4, and most preferably against the four serotypes. For example, a vaccine composition for use in a booster vaccination according to the present invention results in a vaccine efficacy (after booster) in respect of dengue disease caused by any serotype (in a human subject as defined herein) of at least 30%, more preferably at least 40%, more preferably at least 50%, more preferably 60% and even more preferably 70%. For example, a vaccine composition for use in a booster vaccination according to the present invention results in a vaccine efficacy (after booster) in respect of dengue disease caused by serotype 1, serotype 2, serotype 3 or serotype 4 (in a human subject as defined herein) of at least 30%, more preferably at least 40%, more preferably at least 50%, more preferably 60% and even more preferably 70%.

(37) Preferably, said dengue disease caused by a dengue virus is severe dengue disease. Preferably, the method of the invention results in a reduction in the incidence or likelihood of hospitalisation due to dengue disease caused by a dengue virus, irrespective of the dengue virus serotype. Preferably, said dengue disease caused by a dengue virus is DHF.

(38) A vaccine composition according to the 1.sup.st aspect of the present invention is administered as a booster to a human subject who has already received a primary vaccination regimen against dengue virus; the vaccine composition is thus administered to a human subject who is preferably at least 2 years old. Preferably said human subject is at least 5 years old. Preferably said human subject is at least 7 years old, even more preferably said human subject is at least 9 years old.

(39) Most preferably, especially when the primary vaccination consists in a 3-dose regimen, administered around 6 months apart from each other, the human subject to be administered the booster dose according to the 1.sup.st aspect of the invention, is at least 10 years old, or even more preferably 11 years old. Preferably said human subject is at least 11 or 12 years old.

(40) The vaccine composition according to the 1.sup.st aspect is administered to a subject who is preferably less than 62 years old, preferably less than 55, and even more preferably less than 47 years old. A preferred subject according to this aspect of the invention is thus aged between 2 years and 62 years, preferably between 5 years and 55 years, and more preferably between 11 years and 47 years.

(41) A vaccine composition according to the 2.sup.nd aspect of the invention, which is to be administered as a primary vaccination followed by a booster vaccination, is to be administered to a human subject who is preferably at least 9 months old. Preferably said human subject is at least 2 years old, or 4 or 5 years old. Preferably said human subject is at least 7 years old, even more preferably said human subject is at least 9 years old.

(42) The vaccine composition according to the 2.sup.nd aspect is administered to a subject who is preferably less than 60 years old, preferably less than 55, and even more preferably less than 45 years old. A preferred subject according to this aspect of the invention is thus aged between 9 months and 60 years, preferably between 4 years and 55 years, and more preferably between 9 years and 45 years

(43) Alternatively, according to both aspects of the invention, said human subject is aged between 2 and 60 years old. Preferably said human subject is aged between 10 and 60 years old, for example between 10 and 50 years old. According to a preferred embodiment, said human subject is aged between 11 and 50 years old. According to an even more preferred embodiment, the subject is aged between 12 and 45 years old, for example between 12 and 30 years old.

(44) A human subject according to the present invention is preferably not pregnant, lactating or of childbearing potential, does not have self-reported or suspected congenital or acquired immunodeficiency, has not been in receipt of immunosuppressive therapy within the 6 months prior to vaccination or systemic corticosteroids therapy for more than 2 weeks within the 3 months prior to vaccination, is not HIV seropositive and does not have systemic hypersensitivity to any of the vaccine components as defined herein.

(45) A vaccine composition of the present invention is administered as a booster vaccination, or as a primary vaccination followed by a booster vaccination, to a human subject who is yellow fever immune or yellow fever naïve, preferably yellow fever naïve. As used herein, a yellow fever immune subject refers to a subject who has been infected by a YF virus or immunized by a YF vaccine before administration of the primary vaccination or booster composition of the present invention, i.e. a serum sample taken from said subject will produce a positive result in a YF ELISA or YF PRNT.sub.50 assay. Conversely, a yellow fever naïve subject refers to a subject who has not been infected by a YF virus or immunized by a YF vaccine before administration of the vaccine or booster composition of the invention, i.e. a serum sample taken from said subject will produce a negative result in a YF ELISA or YF PRNT.sub.50 assay. Briefly, a YF PRNT.sub.50 assay is carried out as follows. Serial two-fold dilutions of serum to be tested (previously heat-inactivated) are mixed with a constant concentration of the YF vaccinal strain 17D (expressed as PFU/mL). The mixtures are inoculated in duplicate into wells of a plate of confluent Vero cells. After adsorption, cell monolayers are overlaid and incubated for a few days. The reported value (end point neutralization titre) represents the highest dilution of serum at which ≥50% of YF challenge virus (in plaque counts) is neutralized when compared to the negative control wells, which represents the 100% virus load. The LLOQ for the YF PRNT.sub.50 assay is 10 (1/dil).

(46) Preferably a vaccine composition of the present invention is administered as a booster vaccination to a human subject who is yellow fever naïve and dengue immune, more specifically to a subject who has not been infected by a YF or dengue virus, has not been immunized by a YF vaccine but has been immunized by a dengue vaccine before administration of the booster composition of the present invention.

(47) The primary vaccination course according to both aspects of the present invention may be administered in one dose or in multiple doses, for example in one, two or three doses. When the primary vaccination consists in three doses, the first dose and the third dose are preferably administered approximately twelve months apart. For instance, a primary vaccination may consist in a first dose, a second dose and a third dose, wherein said second dose is to be administered about six months after said first dose and wherein said third dose is to be administered about twelve months after said first dose. Alternatively, the three doses may be administered at zero months, at about three to four months (e.g. at about three-and-a-half months) and at about twelve months (i.e. a regimen wherein the second dose of the primary vaccination is administered at about three-and-a-half months after the first dose, and wherein the third dose of the primary vaccination is administered at about twelve months after the first dose).

(48) A primary vaccination according to both aspects of the present invention may consist in two doses. Preferably, the first dose and the second dose are administered approximately about three, six, eight or nine months apart. Preferably, the second dose is administered about six months after the first dose. Alternatively, two doses may be administered to a subject simultaneously or almost simultaneously (e.g. within 24 hours of each other).

(49) A primary vaccination according to both aspects of the present invention may also consist of a single dose.

(50) The booster vaccination according to the invention may also be administered in one or several doses, preferably in one, two or three doses. All the different variations disclosed above with respect to the primary vaccination apply mutatis mutandis to the booster vaccination. According to a preferred embodiment, the vaccine composition of the invention is administered as a single booster dose.

(51) Preferably, according to the present invention, the vaccine composition administered as a booster vaccination is to be administered at least one year after the end of the primary vaccination course, i.e. the first dose of the booster is administered at least one year after administration of the last dose scheduled in the initial immunization regimen, more preferably at least two years after the primary vaccination course, and even more preferably around 4 to 6 years after the primary vaccination.

(52) According to a preferred embodiment, the booster vaccination is administered less than 20 years after the end of the primary vaccination, i.e. the first dose of the booster is administered less than 20 years after administration of the last dose scheduled in the initial immunization regimen. For example, the booster administration is administered between 1 year and 20 years after the end of the primary vaccination course, preferably between 1.5 and 15 years after the end, more preferably between 2 years and 10 years after the end of the primary vaccination course. More preferably, the booster vaccination is administered between around 4 years after the end of the primary vaccination and about 8 years, more preferably around 4 to 5 years after the end of the primary vaccination.

(53) In the context of the present invention, the booster vaccination may also advantageously be repeated, i.e. administered more than once, for example twice, or three times. Preferably the booster vaccination is repeated around every 4 or 5 years after the first booster vaccination, or every 7 years, or every 10 years.

(54) A human subject according to the present invention (to which a vaccine composition is administered as a booster) is preferably resident in or travelling to a dengue endemic area. More preferably, said human subject is resident in a dengue endemic area. A human subject according to the present invention may also be resident in an area that is experiencing a dengue epidemic. The term resident is given its conventional meaning herein and refers to a person who is normally domiciled in the area in question. Dengue endemic areas are well-known to a person of skill in the art and include, according to the present invention, most of the tropics and sub-tropics, for instance any country identified as an endemic country by the WHO. For instance, a dengue endemic area according to the present invention may comprise those American countries or parts thereof which fall within the tropics and sub-tropics. A dengue endemic area according to the present invention may thus comprise any one or more of the following countries or parts thereof: Brazil, Venezuela, Colombia, Ecuador, Peru, Bolivia, Paraguay, Panama, Costa Rica, Nicaragua, Honduras, El Salvador, Guatemala, Belize, Mexico, the USA and the islands of the Caribbean. In a particular embodiment, a dengue endemic area of the present invention may consist of the following: Brazil, Colombia, Honduras, Mexico and Puerto Rico. In another particular embodiment, a dengue endemic area of the present invention may consist of the following: Brazil, Colombia and Honduras. A dengue endemic area according to the present invention may also include south Asian and Oceania countries within the tropics and sub-tropics. A dengue endemic area according to the present invention may thus consist of any one or more of the following: India, Myanmar (Burma), Thailand, Laos, Viet Nam, Cambodia, Indonesia, Malaysia, Singapore, the Philippines, Taiwan, Papua New Guinea and Australia. A dengue endemic area according to the present invention, (which may be national or subnational), is an area where epidemiological data indicate a high burden of disease. For example, a dengue endemic area may be defined as an area wherein the dengue seroprevalence rate in the population targeted for vaccination is at least 50%, at least 60%, at least 70%, at least 80% or at least 90%. In a preferred embodiment, a subject according to the present invention is resident in an area where the dengue seroprevalence in local population aged nine years old is at least 50%, more preferably at least 70%. In this regard, it is considered that older sub-populations exhibit greater seroprevalence rates, since as age increases, the likelihood of having been infected with a dengue virus increases.

(55) When the vaccine composition to be used in a method according to the present invention comprises dengue antigens of serotypes 1 to 4 which comprise nucleic acid sequences having at least 90%, at least 95%, at least 98% or 100% identity to SEQ ID NOs: 1, 2, 3 and 4 respectively (for example the dengue antigens CYD1, CYD2, CYD3 and CYD4), a human subject according to the present invention (to which a vaccine composition of the present invention is administered) is advantageously resident in a dengue endemic area in which the dominant circulating strains of dengue are of serotypes 1, 3 and 4. For example, at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the cases of dengue disease in said dengue endemic area are caused by a dengue virus of serotypes 1, 3 or 4. A human subject according to the present invention (to which a vaccine composition of the present invention is administered) is advantageously resident in a dengue endemic area in which the dominant circulating strains of dengue are of serotypes 3 and 4. For example, at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the cases of dengue disease in said dengue endemic area are infections by a dengue virus of serotype 3 or 4.

(56) When the vaccine composition to be used in a method according to the present invention comprises dengue antigens of serotypes 1 to 4 which comprise nucleic acid sequences having at least 90%, at least 95%, at least 98% or 100% identity to SEQ ID NOs: 1, 2, 3 and 4 respectively (for example the dengue antigens CYD1, CYD2, CYD3 and CYD4), a human subject according to the present invention (to which a vaccine composition of the present invention is administered) is advantageously resident in a dengue endemic area in which the circulating dengue strain of serotype 2 has a genotype which is characterised by the presence of Thr and Gly at positions E-226 and E-228. Advantageously, the circulating dengue strain of serotype 2 has a genotype which is characterised by the presence of at least five of or all six of the following residues Arg, Asn, Asp, Thr, Gly and His at positions prM-16, E-83, E-203, E-226, E-228 and E-346 respectively, wherein the residues at positions E-226 and E-228 must be Thr and Gly respectively. In this context, prM-16 designates position 16 of the prM protein and E-83 designates position 83 of the E protein etc. A human subject according to the present invention (to which a vaccine composition of the present invention is administered) is preferably resident in a dengue endemic area in which the circulating serotype 2 dengue virus has a genotype as defined in this paragraph, i.e. at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or 100% of the cases of dengue disease of serotype 2 in said dengue endemic area are caused by dengue virus of serotype 2 having said genotype. Dengue disease caused by a dengue virus of serotype 2, as referred to herein, is preferably dengue disease caused by a dengue virus of serotype 2 having a genotype as defined in this paragraph.

(57) When the vaccine composition to be used in a method according to the present invention comprises dengue antigens of serotypes 1 to 4 which comprise nucleic acid sequences having at least 90%, at least 95%, at least 98% or 100% identity to SEQ ID NOs: 1, 2, 3 and 4 respectively (for example the dengue antigens CYD1, CYD2, CYD3 and CYD4) a human subject according to the present invention (to which a vaccine composition of the present invention is administered) is advantageously resident in a dengue endemic area in which the circulating dengue strain of serotype 2 does not have an Asian-1 genotype. Dengue viruses of serotype 2 can be sub-divided into several genotypes, which are referred to as: American, Asian/American, Asian-1, Asian-2, Cosmopolitan and Sylvatic (Twiddy S S et al. (2002) Phylogenetic relationships and differential selection pressures among genotypes of dengue-2 virus. Virology; 298(1): 63-72). Thus, a human subject according to the present invention (to which a vaccine composition of the present invention is administered) is advantageously resident in a dengue endemic area in which the circulating dengue strain of serotype 2 has an American, Asian/American, Asian-2, Cosmopolitan or Sylvatic genotype. More preferably, a human subject according to the present invention (to which a vaccine composition of the present invention is administered) is advantageously resident in a dengue endemic area in which the circulating dengue strain of serotype 2 has an American, Asian/American, or Cosmopolitan genotype. A human subject according to the present invention (to which a vaccine composition of the present invention is administered) is preferably resident in a dengue endemic area in which the circulating serotype 2 dengue virus has a genotype as defined in this paragraph, i.e. at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or 100% of the cases of dengue disease of serotype 2 in said dengue endemic area are caused by dengue virus of serotype 2 having an American, Asian/American, Asian-2, Cosmopolitan or Sylvatic genotype, preferably an American, Asian/American or Cosmopolitan genotype. Dengue disease caused by a dengue virus of serotype 2, as referred to herein, is preferably dengue disease caused by a dengue virus of serotype 2 having an American, Asian/American, Asian-2, Cosmopolitan or Sylvatic genotype. More preferably, dengue disease caused by a dengue virus of serotype 2, as referred to herein, is preferably dengue disease caused by a dengue virus of serotype 2 having an American, Asian/American, or Cosmopolitan genotype. The genotype of a particular dengue-2 virus strain is determined by sequence alignment and phylogenetic tree analysis. Briefly, reference sequences (which are selected nucleotide sequences encoding the E proteins of a representative strain of each genotype as described in Twiddy et al.) are aligned with the nucleotide sequences encoding the E proteins of the serotype-2 strains to be genotyped. Then a phylogenetic tree is calculated and a genotype is assigned to each unknown serotype-2 strain according to their respective clustering with the reference-genotype sequences. Phylogenetic trees are calculated according to the maximum likelihood method using FastTree 2 software (Price M N et al., FastTree 2-approximately maximum-likelihood trees for large alignments, PLoS One. 2010; 5(3): e9490) and the Whelan and Goldman model of amino acid evolution (Whelan S, Goldman N. A general empirical model of protein evolution derived from multiple protein families using a maximum-likelihood approach. Mol. Biol. Evol. 2001; 18(5): 691-699).

(58) When the vaccine composition to be used in a method according to the present invention comprises dengue antigens of serotypes 1 to 4 which comprise nucleic acid sequences having at least 90%, at least 95%, at least 98% or 100% identity to SEQ ID NOs: 1, 2, 3 and 4 respectively (for example the dengue antigens CYD1, CYD2, CYD3 and CYD4), a human subject according to the present invention (to which a vaccine composition of the present invention is administered) is advantageously resident in a dengue endemic area in which the circulating dengue strain of serotype 4 is of the DEN4-II genotype. In particular, a circulating dengue strain of serotype 4 preferably has residues at “signature” positions pr73, M65, E46, E120, E160, E203, E329, E429, E455, E461 and E478 which match with the equivalent residues in the prM, M and E protein sequences of CYD4 as may be easily derived from SEQ ID NO: 4. Preferably, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9 or all 10 of the “signature” residues must match. M65 refers to position 65 of the M protein and pr73 refers to position 73 of the prM protein etc. A human subject according to the present invention (to which a vaccine composition of the present invention is administered) is preferably resident in a dengue endemic area in which the circulating serotype 4 dengue virus has a DEN4-II genotype as defined in this paragraph, i.e. at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or 100% of the cases of dengue disease of serotype 4 in said dengue endemic area are caused by dengue virus of serotype 4 having said genotype. Dengue disease caused by a dengue virus of serotype 4, as referred to herein, is preferably dengue disease caused by a dengue virus of serotype 4 having a genotype as defined in this paragraph.

(59) When the vaccine composition to be used in a method according to the present invention comprises dengue antigens of serotypes 1 to 4 which comprise nucleic acid sequences having at least 90%, at least 95%, at least 98% or 100% identity to SEQ ID NOs: 1, 2, 3 and 4 respectively (for example the dengue antigens CYD1, CYD2, CYD3 and CYD4), a human subject according to the present invention (to which a vaccine composition of the present invention is administered) is advantageously resident in a dengue endemic area in which the circulating dengue strains of serotypes 1, 2, 3 and 4 comprise prM-E nucleotide sequences which have at least 90%, at least 95%, at least 98% or 100% identity to SEQ ID NOs: 1, 2, 3 and 4 respectively.

(60) Preferably, a booster vaccination according to the present invention, i.e. a composition for use in a method according to the first or the second aspect of the present invention, reduces the incidence or likelihood of dengue disease.

(61) Preferably, a booster vaccination according to the present invention, i.e. a composition for use in a method according to the first or the second aspect of the present invention, results in the prevention of (i.e. is for use in the prevention of) dengue disease caused by dengue virus serotypes 1, 2, 3 and 4 in individuals 9 through 60 years of age, or 9 through 45 years of age, living in endemic areas. In this context, an individual is understood to be a human subject.

(62) Preferably, a booster vaccination according to the present invention, i.e. a composition for use in a method according to the first or the second aspect of the present invention, results in the prevention of (i.e. is for use in the prevention of) dengue disease caused by dengue virus serotypes 1, 2, 3 and 4 in individuals 12 through 60 years of age, or 12 through 45 years of age, living in endemic areas. In this context, an individual is understood to be a human subject.

(63) The exact quantity of a live attenuated dengue virus or a live attenuated chimeric dengue virus of the present invention to be administered in a primary vaccination or in a booster vaccination may vary according to the age and the weight of the subject being vaccinated, the frequency of administration as well as the other ingredients in the composition. Generally, the quantity of a live attenuated dengue virus (e.g. VDV1 or VDV2) comprised in a dose of a vaccine composition of the present invention, for primary or booster vaccination, lies within a range of from about 10.sup.3 to about 10.sup.6 CCID.sub.50, for example within a range of from about 5×10.sup.3 to about 5×10.sup.5, for example about 10.sup.4 CCID.sub.50. The quantity of a chimeric dengue virus (such as a chimeric YF/dengue virus or a Chimerivax® (CYD) virus) comprised in a vaccine composition of the present invention, for primary or booster vaccination, lies within a range of about 10.sup.5 CCID.sub.50 to about 10.sup.6 CCID.sub.50. The quantity of a live attenuated dengue virus or live attenuated chimeric dengue virus of each of serotypes 1 to 4 comprised in a tetravalent dosage form or bivalent dosage forms according to the present invention is preferably equal. Advantageously, a vaccine composition for use according to the present invention in a primary or booster vaccination comprises an effective amount of a dengue antigen as defined herein.

(64) A vaccine composition for use in a booster vaccination according to the 1.sup.st aspect of the present invention, or for use in a primary vaccination followed by a booster vaccination according to the 2.sup.nd aspect, may further comprise a pharmaceutically acceptable carrier or excipient. A pharmaceutically acceptable carrier or excipient according to the present invention means any solvent or dispersing medium etc., commonly used in the formulation of pharmaceuticals and vaccines to enhance stability, sterility and deliverability of the active agent and which does not produce any secondary reaction, for example an allergic reaction, in humans. The excipient is selected on the basis of the pharmaceutical form chosen, the method and the route of administration. Appropriate excipients, and requirements in relation to pharmaceutical formulation, are described in “Remington's Pharmaceutical Sciences” (19th Edition, A. R. Gennaro, Ed., Mack Publishing Co., Easton, Pa. (1995)). Particular examples of pharmaceutically acceptable excipients include water, phosphate-buffered saline (PBS) solutions and a 0.3% glycine solution. A vaccine composition according to the present invention may advantageously comprise 0.4% saline.

(65) A vaccine composition for use as a booster in a method of the present invention may optionally contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions, such as pH adjusting and buffering agents, tonicity adjusting agents, wetting agents and the like, for example, sodium acetate, sodium lactate, sodium chloride, potassium chloride, calcium chloride, sorbitan monolaurate, triethanolamine oleate, human serum albumin, essential amino acids, nonessential amino acids, L-arginine hydrochlorate, saccharose, D-trehalose dehydrate, sorbitol, tris (hydroxymethyl) aminomethane and/or urea. In addition, the vaccine composition may optionally comprise pharmaceutically acceptable additives including, for example, diluents, binders, stabilizers, and preservatives. Preferred stabilizers are described in WO 2010/003670.

(66) As appreciated by skilled artisans, a vaccine composition for use as a booster according to the first or 2.sup.nd aspect of the present invention, is suitably formulated to be compatible with the intended route of administration. Examples of suitable routes of administration include for instance intramuscular, transcutaneous, subcutaneous, intranasal, oral or intradermal. Advantageously, the route of administration is subcutaneous.

(67) The vaccine compositions for use according to the first or 2.sup.nd aspect of the present invention may be administered using conventional hypodermic syringes or safety syringes such as those commercially available from Becton Dickinson Corporation (Franklin Lakes, N.J., USA) or jet injectors. For intradermal administration, conventional hypodermic syringes may be employed using the Mantoux technique or specialized intradermal delivery devices such as the BD Soluvia™ microinjection system (Becton Dickinson Corporation, Franklin Lakes, N.J., USA), may be used.

(68) The volume of a vaccine composition administered will depend on the method of administration. In the case of subcutaneous injections, the volume is generally between 0.1 and 1.0 ml, preferably approximately 0.5 ml.

(69) According to one embodiment, the invention also provides a kit comprising a vaccine composition of the invention and instructions for the use of said vaccine composition as a booster vaccination according to the first aspect of the invention, or as a primary vaccination and a booster vaccination according to the 2.sup.nd aspect, in a method of protecting a human subject against dengue disease. The kit may comprise said vaccine composition in the form of a single tetravalent dosage form or said kit may comprise said vaccine composition in the form of two bivalent dosage forms. The kit can comprise at least one dose (typically in a syringe) of any vaccine composition contemplated herein. According to one embodiment the kit may comprises a multi-dose formulation of any vaccine composition as described herein. The kit further comprises a leaflet mentioning the use of the said vaccine composition for the prevention of dengue disease or the use of the said vaccine for the prophylaxis of dengue disease, as a booster vaccination or as a primary vaccination and a booster vaccination. The leaflet may further mention the vaccination regimen and the human subject population to be vaccinated, namely subjects who have not previously been naturally infected by a dengue virus, irrespective of the serotype.

(70) The efficacy of a booster composition of the present invention in reducing the likelihood or severity of dengue disease may be measured in a number of ways. For instance, the efficacy of a booster composition of the present invention in reducing the likelihood or severity of dengue disease may be calculated by measuring after the administration of at least one dose of said booster composition (e.g. after administration of one, two or three doses of said booster composition): (i) the number of cases of dengue disease caused by dengue virus of any serotype; (ii) the number of severe dengue cases caused by dengue virus of any serotype; (iii) the number of DHF cases caused by dengue virus of any serotype; and/or (iv) the number of hospitalized cases of dengue disease caused by dengue virus of any serotype;
in a group of subjects that has received said booster composition, and comparing those measurements with the equivalent measurements from a control group of subjects that has not received said booster composition, wherein the subjects in both said groups are resident in a dengue endemic region, have received a primary vaccination and have not been naturally infected by a dengue virus. A statistically conclusive reduction in any one or more of (i) to (iv) in the group of subjects receiving the booster when compared with the control group of subjects not receiving the booster, is indicative of the efficacy of a booster composition according to the present invention.

(71) The efficacy of a booster composition according to the present invention in reducing the severity or likelihood of dengue disease may also be calculated by measuring after the administration of at least one dose of said booster composition (e.g. after administration of one, two or three doses of said booster composition): (i) the mean duration and/or intensity of fever; (iii) the mean value for plasma leakage as defined by a change in haematocrit; (iii) the mean value for thrombocytopenia (platelet count); and/or (iv) the mean value of the level of liver enzymes including alanine aminotransferase (ALT) and aspartate aminotransferase (AST);
in a group of subjects that has received said booster composition and who have developed virologically-confirmed dengue disease after the administration of the booster, and comparing those measurements with the equivalent measurements from a control group of subjects that has not received said booster composition and who have developed virologically-confirmed dengue disease, wherein the subjects in both said groups have received a primary vaccination and have not been naturally infected by a dengue virus before the booster. A statistically significant reduction in any one or more of (i) to (iv) in the group of subjects who have received the booster dose and have developed virologically-confirmed dengue disease when compared with the control group of subjects who have not received the booster and have developed virologically-confirmed dengue disease is indicative of the efficacy of a booster composition according to the present invention in reducing the severity or likelihood of dengue disease.

(72) The efficacy of a booster composition according to the present invention in reducing the severity or likelihood of dengue disease may also be calculated by measuring after the administration of at least one dose of said booster composition (e.g. after administration of one, two or three doses of said booster composition) the neutralising antibody titre induced by said booster composition in a group of subjects that has received said booster composition and using a correlate of risk or a correlate of protection (if available) to convert the neutralizing antibody titre into a measure of efficacy.

(73) Alignments of the nucleic sequences disclosed herein with other nucleic acid sequences may be achieved by any of the suitable sequence alignment methods well known to a person skilled in the art. For example, sequence alignments may be carried out by hand. More conveniently, an alignment may be carried out using a specialised computer program. For example, optimal sequence alignment can be achieved and percent identity can be determined by global sequence alignment algorithms such as the Multiple Sequence Alignment (MSA) algorithms Clustal W and Clustal Omega algorithms, or the Multiple Sequence Comparison by Log-Expectation (MUSCLE) algorithm (Edgar R C, Nucl. Acids Res. (2004): 32 (5): 1792). These algorithms are available on the European Bioinformatics Institute (EBI) web site at http://www.ebi.ac.uk/services. Where such algorithms have user-defined parameters, the default parameters should be used.

(74) It is understood that the various features and preferred embodiments of the present invention as disclosed herein may be combined together.

(75) Throughout this application, various references are cited. The disclosures of these references are hereby incorporated by reference into the present disclosure.

(76) The present invention will be further illustrated by the following examples. It should be understood however that the invention is defined by the claims, and that these examples are given only by way of illustration of the invention and do not constitute in any way a limitation thereof.

EXPERIMENTAL SECTION

(77) CYD64 Clinical Trial: Immunogenicity and Safety of a Tetravalent Dengue Vaccine Given as a Booster Injection in Adolescents and Adults Who Previously Completed the 3-Dose Schedule in a Study Conducted in Latin America.

(78) 1) Summary

(79) The aim of the study is to assess and describe the booster effect of a CYD dengue vaccine dose administered 4 to 5 years after the completion of a 3-dose vaccination schedule.

(80) Primary Objective

(81) To demonstrate the non-inferiority, in terms of geometric mean of titer ratios (GMTRs), of a CYD dengue vaccine booster compared to the third CYD dengue vaccine injection in subjects from previous CYD dengue vaccine trials.
Secondary Objectives: If the primary objective of non-inferiority is achieved: To demonstrate the superiority, in terms of GMTRs, of a CYD dengue vaccine booster compared to the third CYD dengue vaccine injection in subjects from previous CYD dengue vaccine trials. To describe the immune responses elicited by a CYD dengue vaccine booster and placebo injection in subjects who received 3 doses of the CYD dengue vaccine in previous CYD dengue vaccine trials. To describe the neutralizing Antibodies (Ab) levels of each dengue serotype post-dose 3 (previous CYD dengue vaccine trials' subjects) and immediately prior to booster or placebo injection in all subjects. To describe the neutralizing Ab persistence 6 months and 1 year post booster or placebo injection in all subjects. To evaluate the safety of booster vaccination with the CYD dengue vaccine in all subjects.
Primary Outcome Measures: Neutralizing antibody levels against each dengue virus serotype measured 28 days after the third CYD dengue vaccine injection and 28 days after the booster injection in the study group [Time Frame: Day 28 post booster vaccination].
Secondary Outcome Measures: Neutralizing antibody levels against each of the 4 parental dengue virus strains of the CYD dengue vaccine immediately prior and 28 days post booster or placebo injection [Time Frame: Before and Day 28 post booster vaccination] Neutralizing antibody levels against each of the 4 parental dengue virus strains of the CYD dengue vaccine 6 months and 1 year post booster or placebo injection [Time Frame: 6 months and 12 months post booster vaccination] Percentages of subjects with seroconversion 28 days after the booster injection for each of the four parental dengue virus strain of CYD dengue vaccine: percentages of subjects with either a pre-booster titer <10 (1/dil) and a post-booster titer 40 (1/dil), or a pre-booster titer 10 (1/dil) and a 4-fold increase in post-booster titer as determined by PRNT immediately prior and 28 days post-booster or placebo injection [Time Frame: Before and Day 28 post booster vaccination] Number of participants reporting solicited injection site reactions, solicited systemic reactions, unsolicited adverse events, and serious adverse events occurring during trial [Time Frame: Day 0 up to 2 years post vaccination] Solicited injection site reactions: Pain, Erythema, and Swelling. Solicited systemic reactions: Fever (temperature), Headache, Malaise, Myalgia, and Asthenia Neutralizing antibody levels against each dengue virus serotype are measured using dengue plaque reduction neutralization test (PRNT).

(82) 2) Statistical Methods

(83) Hypothesis and Statistical Method for the Primary Objective (Group 1 only) Hypotheses:

(84) Individual Hypotheses for Each Serotype:

(85) A non-inferiority testing approach was performed for each serotype to demonstrate the non-inferiority, in terms of GMTRs, 28 days post-injection, of a CYD dengue vaccine booster dose compared to the third CYD dengue vaccine dose in subjects from CYD13 (Villar L A, et al, 2013, Pediatr Infect Dis J; 32(10):1102-1109) and CYD30 (Dayan G H, et al, 2013, Am J Trop Med Hyg 2013; 89(6): 1058-1065) trials.

(86) Individual hypotheses for each serotype were as follows:

(87) H.sub.0.sup.i:GM(V.sub.Booster.sup.i/V.sub.PD3.sup.i)≤½

(88) H.sub.1.sup.i:GM(V.sub.Booster.sup.i/V.sub.PD3.sup.i)>½

(89) Where i=1, 2, 3 and 4; V.sub.Booster.sup.i is the immunogenicity titer 28 days after the CYD dengue vaccine booster dose and V.sub.PD3.sup.i is the immunogenicity titer 28 days after the third CYD dengue vaccine dose in CYD13 and CYD30 subjects.

(90) Overall Hypothesis:

(91) The overall null hypothesis can be stated as for at least 1 serotype, the post booster dose response (28 days after the CYD dengue vaccine booster injection) is inferior to the PD3 response (28 days after the third CYD dengue vaccine dose in CYD13 and CYD30 subjects)

(92) H.sub.0.sup.G at least one H.sub.0.sup.i not rejected

(93) H.sub.1.sup.G: all H.sub.0.sup.i are rejected

(94) Statistical Methods

(95) A non-inferiority test was performed using the 95% two-sided CI of GM(V.sub.Booster/V.sub.PD3) for each serotype; the 95% CI was calculated using paired t-test.

(96) Subjects with non-missing PD3 and post booster dose titer were included in this analysis. For each serotype, non-inferiority was demonstrated if the lower limit of the two-sided 95% CI was greater than ½. If the null hypothesis is rejected, then the alternative hypothesis of non-inferiority is supported.

(97) The overall null hypothesis was rejected if the four individual null hypotheses were rejected simultaneously.

(98) Hypotheses and Statistical Methods for the First Secondary Objective

(99) As non-inferiority was demonstrated for the primary endpoint, then superiority hypotheses will be performed.

(100) Hypotheses:

(101) Individual Hypotheses for Each Serotype:

(102) A superiority hypothesis testing approach was performed for each serotype to demonstrate the superiority, in terms of GMTRs, 28 days post-injection, of a CYD dengue vaccine booster dose compared to the third CYD dengue vaccine dose in subjects from CYD13 and CYD30 trials. Individual hypotheses for each serotype will be as follows:

(103) H.sub.0.sup.i:GM(V.sub.Booster.sup.i/V.sub.PD3.sup.i)≤1

(104) H.sub.1.sup.i:GM(V.sub.Booster.sup.i/V.sub.PD3.sup.i)>1

(105) Where i=1, 2, 3 and 4; V.sub.Booster.sup.i is the immunogenicity titer 28 days after the CYD dengue vaccine booster dose and is V.sub.PD3.sup.i the immunogenicity titer 28 days after the third CYD dengue vaccine dose in CYD13 and CYD30 subjects.

(106) Overall Hypothesis:

(107) The overall null hypothesis can be stated as for at least 1 serotype, the post booster dose response (28 days after the CYD dengue vaccine booster injection) is not superior to the PD3 response (28 days after the third CYD dengue vaccine dose in CYD13 and CYD30 subjects).

(108) H.sub.0.sup.G at least one H.sub.0.sup.i not rejected

(109) H.sub.1.sup.G: all H.sub.0.sup.i are rejected

(110) Statistical Methods

(111) A superiority test was performed using the 95% two-sided CI of GM(V.sub.Booster/V.sub.PD3) for each serotype; the 95% CI was calculated using paired t-test.

(112) Subjects with non-missing PD3 and post booster dose titer were included in this analysis. For each serotype, superiority was to be demonstrated if the lower limit of the two-sided 95% CI is greater than 1. If the null hypothesis was rejected, then the alternative hypothesis of superiority was supported.

(113) The overall null hypothesis was to be rejected if the four individual null hypotheses were rejected simultaneously.

(114) Statistical Methods for Other Secondary and Additional Objectives

(115) All other analyses are descriptive; no hypotheses are tested.

(116) For immunogenicity, 2 sample t-test on the log.sub.10 transformed titers were used for 95% CI for the ratio of geometric mean titers (GMTs) (difference between GMTs on log scale).

(117) The 95% CIs for percentages were calculated using the exact binomial distribution (Clopper-Pearson's method). Assuming that logo transformation of the titers/titers ratio followed a normal distribution, first, the mean and 95% CIs were calculated on logo (titers/titers ratio) using the usual calculation for normal distribution, then antilog transformations were applied to the results of calculations, to compute GMTs/GMTRs and their 95% CIs.

(118) For safety, the exact binomial distribution (Clopper-Pearson method) for proportions was used in calculations of the 95% CIs.

(119) Calculation of Sample Size:

(120) There was to be 279 subjects in Group 1 and 93 subjects in Group 2. Assuming a dropoutrate of approximately 2% for each group 28 days post injection, a total of 273 and 91 evaluable subjects was anticipated for Groups 1 and 2, respectively. With 273 evaluable subjects, the probability of observing at least 1 AE with true incidence of 1.1% was approximately 95%. Sample size for the primary endpoint (only for Group 1) was estimated to demonstrate non-inferiority, in terms of GMTRs, 28 days post-injection, of a CYD dengue vaccine booster compared to the third CYD dengue vaccine dose in subjects from CYD13 and CYD30 trials. With 273 evaluable subjects in Group 1, the overall power (see Table 1) using paired test to reject the 4 individual null hypotheses simultaneously was expected to be 88.3%; calculation assumed a non-inferiority margin (delta)=2, one-sided type I error=0.025 and correlation between the responses PD3 and post booster dose of the same serotype in the same subject=0.5.

(121) TABLE-US-00001 TABLE 1 Power/Sample size calculation summary table for primary endpoint Component Standard deviation Non-Inferiority Power for (Antigen) (log 10) Definition N = 273 Serotype 1 (sd1 = 0.88, sd2 = 1.76) >1/2 0.902 Serotype 2 (sd1 = 0.70, sd2 = 1.40) >1/2 0.983 Serotype 3 (sd1 = 0.62, sd2 = 1.24) >1/2 0.996 Serotype 4 (sd1 = 0.50, sd2 = 1.00) >1/2 1.000 Overall 0.883

(122) The calculation of the standard deviation for PD3 (sd1) was based on the weighted average of 28-day PD3 standard deviations of titers from the Phase II trials CYD13 and CYD30 and the standard deviation for post booster dose (sd2) was estimated based on standard deviation for PD3.

(123) Since 4 individual null hypotheses should be rejected simultaneously to reject the overall null hypothesis, no multiplicity adjustment for alpha is necessary.

(124) A 3:1 randomization ratio between Group 1 and Group 2 was chosen, so 279 and 93 subjects were expected to be enrolled in Group 1 and Group 2, respectively.

(125) Calculation of Geometric Mean of Titer (GMT) and Geometric Mean of Titer Ratios (GMTR):

(126) The geometric mean of the neutralizing antibody titer was calculated assuming that Log10 transformation of the titers follows a normal distribution, such that the mean and the 95% CI were calculated on Log10 (titers) using the usual calculation for normal distribution (using Student's t distribution with n-1 degree of freedom). The antilog transformation is then applied to the results of calculations, in order to provide geometric mean of titers (GMTs). For the computation of GMTs, a titer reported as below LLOQ is converted to a value of 0.5 LLOQ.

(127) The GM is defined as follows:

(128) $\mathrm{GM}={\left(\underset{i=1}{\overset{n}{.Math.}}{y}_i\right)}^{1/n}={10}^{\frac{1}{n}}\underset{i=1}{\overset{n}{.Math.}}{\log }_{10}\left(y_i\right)$

(129) With respect to Geometric Mean Ratios, they were obtained by first calculating the difference of the log transformed data between two comparable groups, and then the ratios are obtained by anti-log transformation of the difference.

(130) For calculating the geometric mean titer ratio (GMTR), the values below LLOQ are converted to 0.5 LLOQ for a numerator, and the values below LLOQ are converted to LLOQ for a denominator.

(131) This method provides the most conservative results for GMTR.

(132) 3) Method for Assessing the Dengue Neutralizing Antibody Level and Seroconversion:

(133) Dengue neutralizing Ab levels are measured by PRNT (using parental dengue virus strains of CYD dengue vaccine constructs) by Sanofi Pasteur GCI, Swiftwater, USA (or outsourced with a GCI selected external laboratory).

(134) Serial, 2-fold dilutions of serum to be tested (previously heat-inactivated) are mixed with a constant challenge-dose of each dengue virus serotype 1, 2, 3 or 4 (expressed as plaque-forming unit [PFU/mL). The mixtures are inoculated into wells of a microplate with confluent

(135) TABLE-US-00002 TABLE 7A NAb titres against each serotype at PD3, pre-booster injection and 28 days post-booster injection in subjects dengue naïve (non-immune) at baseline (i.e. at D0 in the previous trials CYD13 and CYD30) CYD Dengue Vaccine Placebo Group Group (N = 177) (N = 64) Component Time point/ratio M GM (95% CI) M GM (95% CI) Serotype 1 [PRNT- Post dose 3 in CYD13 and CYD30 (PD3) 40 26.2 (17.0; 40.4) 18 39.9 (19.3; 82.4) 1/dil] V01 (D0) 41 29.6 (15.6; 56.1) 18 54.0 (21.4; 136) V04 (D28) 41 100 (52.5; 192) 18 40.4 (12.6; 130) Ratio V01 (D0)/PD3 40 0.801 (0.431; 1.49) 18 1.16 (0.524; 2.57) Ratio V04 (D28)/PD3 40 2.86 (1.48; 5.51) 18 0.866 (0.318; 2.36) Ratio V04 (D28)/V01 (D0) 41 2.54 (1.57; 4.11) 18 0.616 (0.356; 1.07) Serotype 2 [PRNT- Post dose 3 in CYD13 and CYD30 (PD3) 40 57.1 (39.6; 82.3) 18 79.9 (39.3; 163) 1/dil] V01 (D0) 41 48.9 (25.4; 94.1) 18 55.0 (20.2; 150) V04 (D28) 41 213 (121; 375) 18 61.0 (17.5; 213) Ratio V01 (D0)/PD3 40 0.757 (0.416; 1.38) 18 0.637 (0.201; 2.03) Ratio V04 (D28)/PD3 40 3.45 (1.93; 6.18) 18 0.706 (0.181; 2.75) Ratio V04 (D28)/V01 (D0) 41 3.38 (2.23; 5.12) 18 0.880 (0.415; 1.86) Serotype 3 [PRNT- Post dose 3 in CYD13 and CYD30 (PD3) 41 129 (98.1; 168) 18 138 (82.0; 234) 1/dil] V01 (D0) 41 51.8 (27.4; 97.9) 18 68.3 (28.7; 163) V04 (D28) 41 288 (163; 510) 18 74.8 (27.8; 201) Ratio V01 (D0)/PD3 41 0.403 (0.227; 0.714) 18 0.493 (0.256; 0.950) Ratio V04 (D28)/PD3 41 2.24 (1.30; 3.88) 18 0.540 (0.240; 1.22) Ratio V04 (D28)/V01 (D0) 41 4.55 (2.86; 7.22) 18 0.976 (0.556; 1.71) Serotype 4 [PRNT- Post dose 3 in CYD13 and CYD30 (PD3) 41 103 (65.9; 162) 18 119 (71.9; 197) 1/dil] V01 (D0) 41 54.9 (37.2; 80.9) 18 31.2 (16.1; 60.3) V04 (D28) 41 347 (183; 657) 18 37.0 (17.9; 76.6) Ratio V01 (D0)/PD3 41 0.487 (0.278; 0.854) 18 0.252 (0.133; 0.476) Ratio V04 (D28)/PD3 41 3.08 (1.50; 6.36) 18 0.299 (0.148; 0.604) Ratio V04 (D28)/V01 (D0) 41 5.91 (2.99; 11.7) 18 0.980 (0.632; 1.52)

(136) TABLE-US-00003 TABLE 7B NAb titres against each serotype at PD3, pre-booster injection and 28 days post-booster injection in subjects dengue immune at baseline (i.e. at D0 in the previous trials CYD13 and CYD30) CYD Dengue Vaccine Placebo Group Group (N = 177) (N = 64) Component Time point/ratio M GM (95% CI) M GM (95% CI) Serotype 1 [PRNT- Post dose 3 in CYD13 and CYD30 (PD3) 136 656 (501; 861) 46 463 (278; 771) 1/dil] V01 (D0) 136 668 (498; 895) 46 725 (413; 1273) V04 (D28) 136 940 (723; 1222) 46 650 (358; 1181) Ratio V01 (D0)/PD3 136 1.00 (0.803; 1.25) 46 1.52 (0.913; 2.53) Ratio V04 (D28)/PD3 136 1.41 (1.15; 1.73) 46 1.36 (0.840; 2.21) Ratio V04 (D28)/V01 (D0) 136 1.38 (1.16; 1.65) 46 0.882 (0.668; 1.17) Serotype 2 [PRNT- Post dose 3 in CYD13 and CYD30 (PD3) 135 613 (474; 792) 46 511 (365; 713) 1/dil] V01 (D0) 136 657 (505; 853) 46 647 (408; 1025) V04 (D28) 136 922 (734; 1158) 46 705 (439; 1132) Ratio V01 (D0)/PD3 135 1.07 (0.827; 1.38) 46 1.27 (0.794; 2.02) Ratio V04 (D28)/PD3 135 1.50 (1.17; 1.94) 46 1.38 (0.871; 2.19) Ratio V04 (D28)/V01 (D0) 136 1.38 (1.16; 1.65) 46 1.09 (0.782; 1.52) Serotype 3 [PRNT- Post dose 3 in CYD13 and CYD30 (PD3) 134 1045 (849; 1286) 46 921 (627; 1353) 1/dil] V01 (D0) 136 638 (502; 811) 46 918 (581; 1452) V04 (D28) 136 866 (689; 1089) 46 857 (561; 1311) Ratio V01 (D0)/PD3 134 0.585 (0.483; 0.710) 46 0.997 (0.655; 1.52) Ratio V04 (D28)/PD3 134 0.817 (0.668; 0.999) 46 0.931 (0.617; 1.40) Ratio V04 (D28)/V01 (D0) 136 1.34 (1.12; 1.61) 46 0.934 (0.724; 1.20) Serotype 4 [PRNT- Post dose 3 in CYD13 and CYD30 (PD3) 135 315 (249; 400) 45 346 (253; 475) 1/dil] V01 (D0) 136 224 (186; 269) 46 307 (214; 441) V04 (D28) 136 343 (281; 418) 46 287 (205; 402) Ratio V01 (D0)/PD3 135 0.664 (0.527; 0.838) 45 0.876 (0.584; 1.31) Ratio V04 (D28)/PD3 135 1.03 (0.786; 1.34) 45 0.825 (0.551; 1.24) Ratio V04 (D28)/V01 (D0) 136 1.52 (1.25; 1.86) 46 0.933 (0.744; 1.17)
Vero cell monolayers. After adsorption, cell monolayers are incubated for a few days. The presence of dengue virus infected cells is indicated by formation of plaques. A reduction in virus infectivity due to neutralization by Ab present in serum samples is detected. The reported value (end point neutralization titer) represents the highest dilution of serum at which ≥50% of dengue challenge virus (in plaque counts) is neutralized when compared to the mean viral plaque count in the negative control wells which represents the 100% virus load. The end point neutralization titers are presented as discontinuous values. The lower limit of quantitation (LLOQ) of the assay is 10 (1/dil).

(137) Seroconversion rates 28 days after the booster injection for each of the four parental dengue virus strain of CYD-TDV dengue vaccine, was defined as the percentages of subjects with either a pre-booster titer <10 (1/dil) and a post-booster titer ≥40 (1/dil), or a pre-booster titer ≥10 (1/dil) and a ≥4-fold increase in post-booster titer as determined by PRNT.sub.50 (Plaque Reduction Neutralization Test) immediately prior and 28 days post-booster or placebo injection. The safety profile of the booster dose was also analyzed with no specific findings.

(138) 4) Introduction:

(139) CYD64 is a multi-center, observer-blind, randomized, placebo controlled, Phase II non-inferiority trial conducted in 251 healthy adolescents and adults in Brazil, Colombia, Honduras, Mexico and Puerto Rico, who received one CYD-TDV dengue vaccine (Dengvaxia®) booster dose between Apr. 14, 2016 and Oct. 19, 2016. It was conducted in accordance with the Declaration of Helsinki and the International Conference on Harmonisation guidelines for good clinical practice as well as with all local and/or national regulations. In addition, each study site's Institutional Review Board and Independent Ethics Committee approved the study protocol. No protocol amendments have been done to date. Written informed consent was obtained from all participants and/or participants' parents/guardians before study entry. Eligible participants were healthy adolescents and adults aged 15.3-23.8 years that had received 3 doses of the CYD-TDV dengue vaccine 4-5 years earlier in two previous specific trials (CYD30 and CYD13, NCT01187433 and NCT00993447 respectively). Exclusion criteria included previous vaccination against dengue that was not part of the previous mentioned trials; pregnant, lactating or childbearing potential women; participation at any time of study enrollment in another trial; reception of any vaccine in the 4 weeks preceding the trial vaccination or planned to receipt any vaccine in the 4 week following the trial vaccination; reception of immune globulins, blood or blood-derived products in the past 3 months; known or suspected congenital or acquired immunodeficiency; reception of any immunosuppressive therapy; known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccines used in the trial or to a vaccine containing any of the same substances; chronic illness that, in the opinion of the Investigator, could interfere with trial conduct or completion; deprivation of freedom by an administrative or court order, or in an emergency setting, or hospitalized involuntarily; current alcohol abuse or drug addiction; moderate or severe acute illness/infection on the day of vaccination or febrile illness (temperature≥38.0° C.); identified as an Investigator or employee of the Investigator or study center with direct involvement in the proposed study, or any identified immediate family member.

(140) Each of the 251 participants enrolled in the trial were randomly assigned to one of the two study groups (group 1 or group 2) via an interactive voice response system or interactive web response system according to a 3:1 ratio (3 subjects in the CYD-TDV Dengue Vaccine Group for 1 subject included in the Placebo Group). Randomization was performed with permuted block method with stratification by site. A double randomization system was used, this implies that the subject treatment allocation was separated from doses dispensing. The unique dose numbers was defined according to a random list to ensure that dose numbers could not be used to distinguish between treatment groups. Subject numbers were not reassigned for any reason.

(141) All participants in Group 1 received a CYD-TDV Dengue vaccine and all participants in Group 2 received a placebo injection at enrollment (day 0); also all participants provided 1 pre-injection blood sample at enrollment to assess baseline dengue immune status before the first vaccination, and 1 blood sample 28 days post-injection for dengue immunogenicity. Neutralizing antibodies against each of the 4 parental dengue virus strains were measured 28 days after the third CYD-TDV dengue vaccine injection and 28 days post-booster injection (Group 1 only).

(142) For both groups, neutralizing antibodies (Nabs) against each of the 4 parental dengue virus strains were measured immediately prior the booster or placebo injection. Also, individual post-booster/pre-booster Geometric Mean Titers Ratios (GMTRs) for each of the four parental dengue virus strains of the CYD-TDV dengue vaccine were measured immediately prior and 28 days post-booster or placebo injection.

(143) For both groups, Nabs against each of the 4 parental dengue virus strains were measured 6 months and one year post booster or placebo injection.

(144) 5) Results of the CYD64 Trial, 28 Days Post-Booster Dose

(145) A total of 251 were randomized out of the 372 planned subjects. Following randomization, 187 subjects were allocated to the CYD-TDV Dengue Vaccine Group and 64 subjects to the Placebo Group. The overall distribution of randomized subjects by country and treatment group is summarized in table 2.

(146) TABLE-US-00004 TABLE 2 Subjects randomized per country CYD Dengue Vaccine Group Placebo Group All (N = 187) (N = 64) (N = 251) Country n (%) n (%) n (%) All 187 (100.0) 64 (100.0) 251 (100.0) Brazil 32 (17.1) 11 (17.2) 43 (17.1) Colombia 57 (30.5) 19 (29.7) 76 (30.3) Honduras 32 (17.1) 10 (15.6) 42 (16.7) Mexico 49 (26.2) 18 (28.1) 67 (26.7) Puerto Rico 17 (9.1) 6 (9.4) 23 (9.2)

(147) Overall, at 28 days post-booster injection, 250 (99.6%) subjects were present (i.e. 1 subject from the CYD-TDV Dengue Vaccine Group was absent) and 249 (99.2%) subjects provided a blood sample (i.e., 2 subjects from the CYD-TDV Dengue Vaccine Group did not provide a sample). At 28 days post-booster injection there was only 1 (0.5%) subject who was discontinued from the study. The reason for discontinuation was non-compliance with the protocol.

(148) Non-Inferiority of CYD-TDV Dengue Vaccine Booster Compared to the 3rd CYD-TDV Dengue Vaccine Dose in Previous Trials.

(149) Non-inferiority of dengue Nab after CYD-TDV dengue vaccine booster dose compared to the 3.sup.rd CYD-TDV dengue vaccine dose (PD3) in terms of Dengue PRNT was demonstrated for the 4 serotypes (lower limit of 2-sided 95% CI greater than ½). A Post booster/PD3 ratio with a 95% CI was calculated for each serotype. (Table 3) A covariance analysis of post booster titers against each of the 4 serotypes was done for controlling the baseline Nab levels (removing pre booster effect); a Dengue/Placebo GMT ratio with a 95% CI was calculated for each serotype:serotype 1, ratio 2.04 (1.50; 2.78), p value 0.0004; serotype 2, ratio 1.74 (1.28; 2.38), p value 0.0021; serotype 3, ratio 1.85 (1.37; 2.50), p value 0.0002; and serotype 4, ratio 2.19 (1.53; 3.13), p value<0.0001. This shows that the immunological response is better in the vaccinated group compared with placebo. (Table 4).

(150) Superiority of CYD-TDV Dengue Vaccine Booster Compared to the 3rd CYD-TDV Dengue Vaccine Dose in Previous Trials.

(151) As the overall non-inferiority of the CYD-TDV dengue vaccine booster could be demonstrated, a superiority analysis of the booster dose compared to the third dose of the selected previous trials was performed for each serotype using GMTRs. The superiority of the booster dose was demonstrated for serotype 1, serotype 2, and serotype 4. The superiority of the booster dose could not be demonstrated for serotype 3 as the lower limit of the two-sided 95% CI of the GMTR was <1 for this serotype. (Table 5).

(152) Immune Response 28 Days Post-Booster Injection

(153) At pre-booster injection, GMTs were comparable between treatment groups. They also tended to be within a similar range for serotype 1, serotype 2 and serotype 3. The GMTs of serotype 4 were lower in both groups. After the CYD-TDV dengue vaccine booster injection, GMTs increased as compared to pre-booster injection level. After the placebo injection, pre-booster injection seropositivity rates per serotype tended to remain stable after placebo injection. (Table 6).

(154) TABLE-US-00005 TABLE 3 Non-inferiority of CYD-TDV dengue vaccine booster dose compared to the third CYD-TDV dengue vaccine dose from CYD13 or CYD30-Dengue PRNT-Per-Protocol Analysis Set Post dose 3 in CYD13 and Post booster dose in Ratio CYD30 (PD3) (N = 177) CYD64 (V04) (N = 177) (Post booster/PD3) Non- Component M GM (95% CI) M GM (95% CI) M GM (95% CI) inferiority Serotype 1 [PRNT-1/dil] 176 316 (233; 428) 177 560 (421; 744) 176 1.66 (1.33; 2.06) Yes Serotype 2 [PRNT-1/dil] 175 356 (275; 462) 177 657 (520; 830) 175 1.82 (1.43; 2.31) Yes Serotype 3 [PRNT-1/dil] 175 640 (516; 794) 177 671 (535; 843) 175 1.04 (0.841; 1.27) Yes Serotype 4 [PRNT-1/dil] 176 243 (195; 303) 177 344 (279; 424) 176 1.32 (1.01; 1.74) Yes M: number of subjects with available data at both time points For each serotype, non-inferiority was demonstrated if the lower limit of the two-sided 95% CI for the ratio is greater than ½. Overall non-inferiority will be demonstrated if all 4 serotypes achieve non-inferiority

(155) TABLE-US-00006 TABLE 4 Analysis of covariance of post-booster titers against each of the four serotypes with the parental dengue virus strains-Dengue PRNT-Per- Protocol Analysis Set. CYD Dengue Vaccine Placebo Group p value for p value for Group (N = 177) (N = 64) Difference Ratio baseline*group group*country (95% (95% (Dengue-Placebo) (Dengue/Placebo) interaction interaction Component M LSMEAN CI) M LSMEAN CI) LSMEAN (95% CI) GM (95% CI) term* term* Serotype 1 177 2.74 (2.67; 64 2.43 (2.32; 0.310 (0.176; 2.04 (1.50; 0.0004 0.3250 [PRNT-1/dil] 2.82) 2.55) 0.445) 2.78) Serotype 2 177 2.79 (2.71; 64 2.55 (2.43; 0.242 (0.107; 1.74 (1.28; 0.0021 0.7881 [PRNT-1/dil] 2.86) 2.66) 0.376) 2.38) Serotype 3 177 2.86 (2.79; 64 2.59 (2.48; 0.266 (0.135; 1.85 (1.37; 0.0002 0.1830 [PRNT-1/dil] 2.93) 2.71) 0.398) 2.50) Serotype 4 177 2.55 (2.47; 64 2.21 (2.08; 0.341 (0.186; 2.19 (1.53; 0.0001 0.6498 [PRNT-1/dil] 2.64) 2.35) 0.495) 3.13) M: number of subjects available for the endpoint LSMEAN: least squares of mean Difference in LSMEANS and 95% CI were calculated using the analysis of covariance with pre-booster titer value and country as covariates without any interaction term *p value for the interaction terms were derived from the analysis of covariance on post-booster titers with pre-booster titer value and country as covariates with the interaction term between the pre-booster titers and the randomized group, plus the interaction term between country and the randomized group.

(156) TABLE-US-00007 TABLE 5 Superiority of CYD-TDV dengue vaccine booster dose compared to the third CYD-TDV dengue vaccine dose from previous trials-Dengue PRNT-Full Analysis Set Post dose 3 in CYD13 Post booster dose in and CYD30 (PD3) CYD64 (V04) Ratio (N = 185) (N = 185) (Post booster/PD3) (95% (95% (95% Component M GM CI) M GM CI) M GM CI) Superiority Serotype 1 184 302 (224; 185 536 (404; 184 1.66 (1.34; Yes [PRNT-1/dil] 406) 710) 2.06) Serotype 2 183 340 (264; 185 653 (519; 183 1.90 (1.49; Yes [PRNT-1/dil] 439) 823) 2.41) Serotype 3 183 611 (495; 185 662 (529; 183 1.07 (0.870; No [PRNT-1/dil] 755) 827) 1.31) Serotype 4 184 239 (193; 185 347 (283; 184 1.37 (1.05; Yes [PRNT-1/dil] 295) 426) 1.78) M: number of subjects with available data at both time points For each serotype, superiority will be demonstrated if the lower limit of the two-sided 95% CI for the ratio is greater than 1. Overall superiority will be demonstrated if all 4 serotypes achieve superiority

(157) TABLE-US-00008 TABLE 6 Summary of geometric means of titers and geometric means of individual titer ratios of antibody against each serotype with the parental dengue virus strains at pre- and post-booster injection-Dengue PRNT-Per-Protocol Analysis Set CYD Dengue Vaccine Group Placebo Group (N = 177) (N = 64) Component Time point/ratio M GM (95% CI) M GM (95% CI) Serotype 1 [PRNT- V01 (D0) 177 325 (233; 452) 64 349 (201; 607) 1/dil] V04 (D28) 177 560 (421; 744) 64 297 (162; 547) Ratio V04 (D28)/V01 177 1.59 (1.33; 1.90) 64 0.798 (0.623; (D0) 1.02) Serotype 2 [PRNT- V01 (D0) 177 360 (267; 484) 64 323 (195; 535) 1/dil] V04 (D28) 177 657 (520; 830) 64 354 (205; 610) Ratio V04 (D28)/V01 177 1.70 (1.43; 2.03) 64 1.03 (0.754; (D0) 1.40) Serotype 3 [PRNT- V01 (D0) 177 357 (269; 472) 64 442 (270; 724) 1/dil] V04 (D28) 177 671 (535; 843) 64 432 (266; 700) Ratio V04 (D28)/V01 177 1.78 (1.47; 2.16) 64 0.946 (0.749; (D0) 1.19) Serotype 4 [PRNT- V01 (D0) 177 162 (134; 195) 64 161 (108; 242) 1/dil] V04 (D28) 177 344 (279; 424) 64 161 (110; 237) Ratio V04 (D28)/V01 177 2.09 (1.65; 2.63) 64 0.946 (0.777; (D0) 1.15) M: number of subjects available for the endpoint

(158) The seroconversion rates for 3 of the 4 serotypes were meaningfully different between treatment groups 28 days post-booster injection. The seroconversion rate for serotype 1 was 16.9% (95% CI: 11.7; 23.3) in CYD-TDV Dengue Vaccine Group and 3.1% (95% CI: 0.4; 10.8) in the Placebo Group; for serotype 2, it was 19.2% (95% CI: 13.7; 25.8) and 17.2% (95% CI: 8.9; 28.7); for serotype 3, the seroconversion rate was 20.3% (95% CI: 14.7; 27.0) and 4.7% (95% CI: 1.0; 13.1); and for serotype 4, it was 19.8% (95% CI: 14.2; 26.4) and 6.3% (95% CI: 1.7; 15.2), respectively. One of the plausible explanations of the high seroconversion rate against serotype 2 in the Placebo Group as compared to the CYD-TDV Dengue Vaccine Group is the impact of a natural infection booster effect on GMTs.

(159) Dengue Serostatus at Baseline

(160) The immune response to CYD-TDV dengue vaccine booster injection was analyzed according to the serostatus of subjects at baseline (i.e. at D0 in the previous trials CYD13 and CYD30). Among the 177 subjects enrolled in the CYD-TDV Dengue Vaccine Group, 136 (77%) subjects were dengue-immune at baseline and 41 (23%) were dengue non-immune. In the Placebo Group, there were 46 subjects dengue-immune at baseline and 18 non-immune subjects. Overall, NAb titers against each serotype at PD3, at pre-booster injection, as well as 28 days post-booster injection, were higher in subjects dengue-immune at baseline (Tables 7A and 7B).

(161) Dengue Serostatus at Pre-Booster Injection

(162) At pre-booster injection, GMTs (1/dil) ranged from 224 (serotype 4) to 668 (serotype 1) in dengue-immune subjects and from 29.6 (serotype 1) to 54.9 (serotype 4) in dengue non-immune subjects. At 28 days post-booster injection, GMTs (1/dil) ranged from 343 (serotype 4) to 940 (serotype 1) in dengue-immune subjects and from 100 (serotype 1) to 347 (serotype 4) in dengue non-immune subjects. Dengue serostatus at baseline had a meaningful difference in the seroconversion rate against each serotype. The seroconversion rates were higher in the dengue non-immune group of subjects. (Table 8).

(163) Safety Evaluations

(164) After the CYD-TDV dengue vaccine or the placebo injection, all subjects were assessed for immediate reactions, solicited reactions and unsolicited events or reactions. SAEs were collected throughout the study and serious and non-serious AESIs were collected in defined time-windows according to the type of AESI. An overview of the safety and reactogenicity up to 28 days post-booster injection is provided in table 9.

(165) TABLE-US-00009 TABLE 8 Seroconversion rate against each serotype in dengue immune and non-immune subjects Seroconversion Rate Serotype Dengue Immune Dengue Non-Immune 1 10.3% (95% CI: 5.7; 16.7) 39.0% (95% CI: 24.2; 55.5) 2 13.2% (95% CI: 8.0; 20.1) 39.0% (95% CI: 24.2; 55.5) 3 11.0% (95% CI: 6.3; 17.5) 51.2% (95% CI: 35.1; 67.1) 4 15.4% (95% CI: 9.8; 22.6) 34.1% (95% CI: 20.1; 50.6)

(166) TABLE-US-00010 TABLE 9 Safety overview after booster injection. CYD Dengue Vaccine Group Placebo Group (N = 187) (N = 64) Subjects experiencing at least one: n/M % (95% CI) n/M % (95% CI) Within 30 minutes after booster injection Immediate unsolicited AE 1/187 0.5 (0.0; 2.9) 0/64 0.0 (0.0; 5.6) Immediate unsolicited AR 1/187 0.5 (0.0; 2.9) 0/64 0.0 (0.0; 5.6) Within 28 days after booster injection Solicited reaction 114/187 61.0 (53.6; 68.0) 31/64 48.4 (35.8; 61.3) Solicited injection site reaction 47/187 25.1 (19.1; 32.0) 12/64 18.8 (10.1; 30.5) Solicited systemic reaction 105/187 56.1 (48.7; 63.4) 28/64 43.8 (31.4; 56.7) Unsolicited AE 48/187 25.7 (19.6; 32.6) 13/64 20.3 (11.3; 32.2) Unsolicited AR 2/187 1.1 (0.1; 3.8) 0/64 0.0 (0.0; 5.6) Unsolicited non-serious AE 48/187 25.7 (19.6; 32.6) 13/64 20.3 (11.3; 32.2) Unsolicited non-serious AR 2/187 1.1 (0.1; 3.8) 0/64 0.0 (0.0; 5.6) Unsolicited non-serious injection site AR 1/187 0.5 (0.0; 2.9) 0/64 0.0 (0.0; 5.6) Unsolicited non-serious systemic AE 48/187 25.7 (19.6; 32.6) 13/64 20.3 (11.3; 32.2) Unsolicited non-serious systemic AR 1/187 0.5 (0.0; 2.9) 0/64 0.0 (0.0; 5.6) AE leading to study discontinuationt 0/187 0.0 (0.0; 2.0) 0/64 0.0 (0.0; 5.6) SAE 0/187 0.0 (0.0; 2.0) 0/64 0.0 (0.0; 5.6) Death 0/187 0.0 (0.0; 2.0) 0/64 0.0 (0.0; 5.6) Serious AESI 0/187 0.0 (0.0; 2.0) 0/64 0.0 (0.0; 5.6) Non-serious AESI 0/187 0.0 (0.0; 2.0) 0/64 0.0 (0.0; 5.6) During the study SAE 1/187 0.5 (0.0; 2.9) 0/64 0.0 (0.0; 5.6) Death 0/187 0.0 (0.0; 2.0) 0/64 0.0 (0.0; 5.6) Serious AESI 0/187 0.0 (0.0; 2.0) 0/64 0.0 (0.0; 5.6) n: number of subjects experiencing the endpoint listed in the first column M: number of subjects with available data for the relevant endpoint † Identified in the termination form as SAE or other AE or in an AE form that was at least Grade 1 and was within the time period indicated

(167) Overall, 61.0% of subjects in the CYD-TDV Dengue Vaccine Group and 48.4% in the Placebo Group experienced at least 1 solicited reaction after the booster injection. Among these subjects, 8.0% of subjects in the CYD-TDV Dengue Vaccine Group and 6.3% in the Placebo Group reported at least 1 Grade 3 solicited reaction. The Grade 3 solicited reactions that were reported in each group were mostly systemic reactions. Following the booster injection, the 2 treatment groups were comparable in terms of number, intensity, time of onset, and duration of solicited reactions. The most frequently reported solicited injection site reaction in both groups was injection site pain (24.6% in the CYD-TDV Dengue Vaccine Group and 18.8% in the Placebo Group). One (0.5%) subject experienced an injection site erythema (in the CYD-TDV Dengue Vaccine Group), and no injection site swelling was reported in either group. Most solicited injection site reactions reported were of Grade 1 intensity, occurred within 3 days, and resolved spontaneously within 3 days. One (0.5%) subject in the CYD-TDV Dengue Vaccine Group reported a Grade 3 reaction (injection site pain). The most frequently reported solicited systemic reaction in both groups was headache. At least 1 episode of headache was reported in 46.5% of subjects in the CYD-TDV Dengue Vaccine Group and in 34.4% of subjects in the Placebo Group after injection. The proportions of subjects who reported at least 1 episode of myalgia, malaise, and asthenia were within the same range and were similar across treatment groups (between 21% and 32%). Some 7.9% of subjects in the CYD-TDV Dengue Vaccine Group and 9.5% of subjects in the Placebo Group experienced at least 1 episode of fever. A total of 15 (8.0%) subjects in the CYD-TDV Dengue Vaccine Group and 4 (6.3%) subjects in the Placebo Group experienced at least 1 Grade 3 solicited systematic reaction. Headache was the most frequent Grade 3 systemic reaction, it was reported by 11 (5.9%) subjects from the CYD-TDV Dengue Vaccine Group and by 2 (3.1%) subjects in the Placebo Group. In the CYD-TDV Dengue Vaccine Group, one (0.5%) subject experienced at least 1 immediate unsolicited non-serious AR. The subject experienced a Grade 2 lump in the right axilla. This systemic event spontaneously resolved after 5 days and was assessed as related to the booster injection by the Investigator. Few unsolicited non-serious AEs reported within 28 days after injection were related to vaccination by the Investigator. One subject in the CYD-TDV Dengue Vaccine Group experienced an immediate unsolicited systemic AR (Grade 2 lump in the right axilla). A second subject in the same Group experienced 1 unsolicited non-serious AR (Grade 1 muscular weakness). For both subjects, the ARs occurred within 3 days after booster injection, spontaneously resolved within 4-7 days. Five SAE had been reported, it was considered as not related to vaccination. No AEs considered as significant (i.e., AEs and SAEs leading to discontinuation, AESIs, and hospitalized VCD cases) and None deaths were reported within 28 days after booster injection.

(168) Long Term Follow Up

(169) Persistence of neutralizing antibodies at six months and 1 year post-booster/placebo dose was measured by PRNT in available subjects (both dengue naïve and dengue immune at baseline) and the results are shown by serotype in Tables 10 to 14. As has been seen with other long term follow up analyses of recipients of CYD dengue vaccine, there was a decline in neutralizing antibody titres in the six month period following the administration of Dengvaxia® (booster dose), but after that point, neutralizing antibody titres stabilized, at least until 1 year post booster. Surprisingly, in subjects who were dengue naïve at baseline, the relative rate of decline was lower than in subjects who were dengue immune at baseline. For example, in immune subjects, the GMT levels at 12 months post booster dose for all four serotypes had already fallen below the GMT levels measured just before administration of the booster dose (i.e. at V01/D0). However, in naïve subjects, the GMT levels at 12 months post booster dose for all four serotypes were higher than the GMT levels measured just before administration of the booster dose (i.e. at V01/D0). This result is most easily seen in Table 15, which shows the M12:D0 GMT ratios for each serotype in both baseline naïve and baseline immune subjects. Thus it can be seen that the additive effect of the booster dose in baseline naïve subjects is surprisingly more durable in baseline naïve subjects than in baseline immune patients.

(170) TABLE-US-00011 TABLE 11 Summary of Geometric Mean Titers of antibodies against each serotype with the parental dengue virus strains by baseline dengue status in CYD13/CYD30-Dengue PRNT-Per Protocol Analysis Set. SEROTYPE 1 SEROTYPE 1 [PRNT-1/dil] IMMUNE NAIVE CYD Dengue Vaccine Placebo Group CYD Dengue Vaccine Group Placebo Group Group (N = 177) (N = 64) (N = 177) (N = 64) Time point M GM (95% CI) M GM (95% CI) M GM (95% CI) M GM (95% CI) Post dose 3 in 136 656 (501; 861) 46 463 (278; 771) 40 26.2 (17.0; 40.4) 18 39.9 (19.3; 82.4) CYD13 and CYD30 (PD3) V01 (D0) 136 668 (498; 895) 46 725 (413; 1273) 41 29.6 (15.6; 56.1) 19 54.0 (21.4; 136) V04 (D28) 136 940 (723; 1222) 46 650 (358; 1181) 41 100 (52.5; 192) 18 40.4 (12.6; 130) V05 (M6) 134 469 (362; 607) 45 396 (237; 663) 40 42.4 (25.1; 71.6) 18 31.2 (11.0; 88.2) V06 (M12) 132 473 (366; 611) 46 351 (221; 559) 38 38.6 (23.0; 64.6) 16 29.2 (11.0; 77.9) M: number of subjects available for the endpoint V01 (D0): pre-booster or placebo injection V0 (M6): 6 months post booster or placebo injection GM: Geometric Mean V04 (D28): 28 days post booster or placebo injection V06 (M12): 12 months post booster or placebo injection

(171) TABLE-US-00012 TABLE 12 Summary of Geometric Mean Titers of antibodies against each serotype with the parental dengue virus strains by baseline dengue status in CYD13/CYD30-Dengue PRNT-Per Protocol Analysis Set. SEROTYPE 2 SEROTYPE 2 [PRNT-1/dil] IMMUNE NAIVE CYD Dengue Vaccine Placebo Group CYD Dengue Vaccine Group Placebo Group Group (N = 177) (N = 64) (N = 177) (N = 64) Time point M GM (95% CI) M GM (95% CI) M GM (95% CI) M GM (95% CI) Post dose 3 in 135 613 (474; 792) 46 511 (365; 713) 40 57.1 (39.6; 82.3) 18 79.9 (39.3; 163) CYD13 and CYD30 (PD3) V01 (D0) 136 657 (505; 853) 46 647 (408; 1025) 41 48.9 (25.4; 94.1) 18 55.0 (20.2; 150) V04 (D28) 136 922 (734; 1158) 46 705 (439; 1132) 41 213 (121; 375) 18 61.0 (17.5; 213) V05 (M6) 134 609 (500; 741) 45 617 (435; 873) 40 151 (89.5; 256) 18 72.6 (27.7; 191) V06 (M12) 132 398 (327; 485) 46 388 (288; 523) 38 69.4 (42.3; 114) 16 47.2 (18.1; 123) M: number of subjects available for the endpoint V01 (D0): pre-booster or placebo injection V05 (M6): 6 months post booster or placebo injection GM: Geometric Mean V04 (D28): 28 days post booster or placebo injection V06 (M12): 12 months post booster or placebo injection

(172) TABLE-US-00013 TABLE 13 Summary of Geometric Mean Titers of antibodies against each serotype with the parental dengue virus strains by baseline dengue status in CYD13/CYD30-Dengue PRNT-Per Protocol Analysis Set. SEROTYPE 3 SEROTYPE 3 [PRNT-1/dil] IMMUNE NAIVE CYD Dengue Vaccine Placebo Group CYD Dengue Vaccine Group Placebo Group Group (N = 177) (N = 64) (N = 177) (N = 64) Time point M GM (95% CI) M GM (95% CI) M GM (95% CI) M GM (95% CI) Post dose 3 in 134 1045 (849; 1286) 46 921 (627; 1353) 41 129 (98.1; 168) 18 138 (82.0; 234) CYD13 and CYD30 (PD3) V01 (D0) 136 638 (502; 811) 46 918 (581; 1452) 41 51.8 (27.4; 97.9) 18 68.3 (28.7; 163) V04 (D28) 136 866 (689; 1089) 46 857 (561; 1311) 41 288 (163; 510) 18 74.8 (27.8; 201) V05 (M6) 134 748 (596; 939) 45 776 (503; 1197) 40 132 (79.5; 221) 18 113 (44.5; 284) V06 (M12) 132 433 (347; 540) 46 528 (362; 769) 38 88.0 (54.5; 142) 16 83.4 (34.4; 202) M: number of subjects available for the endpoint V01 (D0): pre-booster or placebo injection V05 (M6): 6 months post booster or placebo injection GM: Geometric Mean V04 (D28): 28 days post booster or placebo injection V06 (M12): 12 months post booster or placebo injection

(173) TABLE-US-00014 TABLE 14 Summary of Geometric Mean Titers of antibodies against each serotype with the parental dengue virus strains by baseline dengue status in CYD13/CYD30-Dengue PRNT-Per Protocol Analysis Set. SEROTYPE 4 SEROTYPE 4 [PRNT-1/dil] IMMUNE NAIVE CYD Dengue Vaccine Placebo Group CYD Dengue Vaccine Group Placebo Group Group (N = 177) (N = 64) (N = 177) (N = 64) Time point M GM (95% CI) M GM (95% CI) M GM (95% CI) M GM (95% CI) Post dose 3 in 135 315 (249; 400) 45 346 (253; 475) 41 103 (65.9; 162) 18 119 (71.9; 197) CYD13 and CYD30 (PD3) V01 (D0) 136 224 (186; 269) 46 307 (214; 441) 41 54.9 (37.2; 80.9) 18 31.2 (16.1; 60.3) V04 (D28) 136 343 (281; 418) 46 287 (205; 402) 41 347 (183; 657) 18 37.0 (17.9; 76.6) V05 (M6) 134 249 (213; 292) 45 247 (193; 315) 40 185 (117; 295) 18 49.9 (26.2; 95.0) V06 (M12) 132 192 (164; 225) 46 193 (157; 238) 38 110 (69.1; 175) 16 37.8 (20.9; 68.3) M: number of subjects available for the endpoint V01 (D0): pre-booster or placebo injection V05 (M6): 6 months post booster or placebo injection GM: Geometric Mean V04 (D28): 28 days post booster or placebo injection V06 (M12): 12 months post booster or placebo injection

(174) TABLE-US-00015 TABLE 15 M12:D0 GMT ratios for each serotype in baseline naïve and baseline immune subjects Baseline naïve Baseline immune Serotype 1 1.30 0.71 Serotype 2 1.42 0.61 Serotype 3 1.70 0.68 Serotype 4 2.00 0.85

CONCLUSIONS

(175) The primary objective of the CYD64 study is met. In subjects having received a 3-dose primary series of the CYD dengue vaccine 4-5 years before, the booster dose is non-inferior to the third dose, in terms of GMTRs. In subjects having received a 3-dose primary series of the CYD dengue vaccine 4-5 years before, the booster dose is not superior to the third dose of the primary series, in terms of GMTRs. Overall superiority is not attained as individual serotypes' superiority is not demonstrated for serotype 3. The CYD dengue vaccine booster increases GMTs of each serotype 28 days after injection. The CYD dengue vaccine booster increases seropositivity rates against each and any serotypes. The dengue serostatus at baseline influences both the persistence of GMTs at pre-booster injection and the level of GMTs post-booster injection; i.e., subjects that were dengue-immune at baseline tended to have higher GMTs both at pre- and post-booster injection. At 28 days after injection, dengue non-immune subjects at baseline have a higher seroconversion rate for each serotype than dengue-immune subjects at baseline; i.e., the increases of GMTs between pre-booster and post-booster injection are greater in subjects that were dengue non-immune (i.e. dengue naïve) at baseline compared to dengue immune subjects at baseline. This difference between dengue immune and dengue non-immune subjects at baseline is also demonstrated in the GMT ratios comparing the GMTs 28 days post booster compared to the GMTs PD3 of the primary vaccination course. The additive effect of the booster dose in baseline naïve subjects is more durable in baseline naïve subjects than in baseline immune patients. A booster injection administered 4-5 years after a 3-dose primary schedule is quite similar, in terms of reactogenicity, to the first CYD dengue vaccine injection administered in CYD13 and CYD30.
Sequences Referred to in this Application:

(176) TABLE-US-00016 TABLE 16 Sequences of the Sequence Listing SEQ ID NO. Sequence 1 prM-E nucleotide sequence of the serotype 1 vaccinal strain which is derived from the PUO 359 (TVP-1140) wild type strain 2 prM-E nucleotide sequence of the serotype 2 vaccinal strain which is derived from the PUO 218 wild type strain 3 prM-E nucleotide sequence of the serotype 3 vaccinal strain which is derived from the PaH881/88 wild type strain 4 prM-E nucleotide sequence of the serotype 4 vaccinal strain which is derived from the 1228 (TVP 980) wild type strain 5 prM-E nucleotide sequence of the serotype 2 vaccinal strain derived from the MD1280 wild type strain (CYD-2V) 6 Entire nucleotide sequence of the VDV1 strain 7 Entire nucleotide sequence of the VDV2 strain

(177) The above listed nucleotide sequences constitute the positive strand RNA of the listed dengue viruses (i.e. the nucleotide sequence which is found in the corresponding viral particles). The equivalent DNA sequences (which may be used to manipulate and express the corresponding virus and which also form part of the disclosure of the present application), can be generated by replacing the nucleotide U with the nucleotide T. Such DNA sequences constitute the cDNA sequences of the corresponding dengue viruses.