Provided is a strain that is effective as an active ingredient of a vaccine against betacoronavirus. This SARS-CoV-2 includes non-structural protein(s) that has the following responsible mutation(s): a mutation in the amino acid residue corresponding to the L of position 445 of SEQ ID NO: 1 in NSP3; a mutation in the amino acid residues corresponding to the G of position 248 and the G of position 416 of SEQ ID NO: 2 in NSP14; and/or a mutation in the amino acid residue corresponding to the V of position 67 of SEQ ID NO: 3 in NSP16.