A SARS-CoV-2 recombinant spike protein vaccine (S-268019-b) for COVID-19 prevention during the Omicron-dominant period: a phase 3, randomised, placebo-controlled clinical trial by Thiem, VD, Anh, PTV, Men, CV, Hung, DT, Pollard, AJ, Kamitani, A, Tada, Y, Fukuyama, H, Iwasaki, Y, Ariyasu, M, Sonoyama, T