Bivalent immunogenic compositions against anthrax and plague are disclosed herein. One bivalent immunogenic composition comprises a triple fusion protein containing three antigens, F1 and V from Yersinia pestis and PA antigen from Bacillus anthracia fused in-frame and retaining structural and functional integrity of all three antigens. Another bivalent immunogenic composition comprises bacteriophage nanoparticles arrayed with these three antigens on the capsid surface of the bacteriophage nanoparticles. These bivalent immunogenic compositions are able to elicit robust immune response in a subject administered said the bivalent immunogenic compositions and provide protection to the subject against sequential or simultaneous challenge with both anthrax and plague pathogens.

It is disclosed herein that viruses coated in silica retain infectivity and the capacity to induce an immune response in an infected host. In addition, silicified virus is remarkably resistant to desiccation. Provided herein are methods of inducing a virus-specific immune response in a subject by administering to the subject an effective amount of silicified virus or silicified virus particles. Methods of enhancing a virus-specific cell-mediated immune response (such as a T cell-mediated immune response) in a subject by administering to the subject a silicified virus or silicified virus particles are also described herein. Further provided are immunogenic compositions comprising silicified virus or silicified virus particles, such as compositions useful as vaccines. The immunogenic compositions include a pharmaceutically acceptable carrier and/or an adjuvant.