A recombinant spike protein subunit vaccine confers protective immunity against SARS-CoV-2 infection and transmission in hamsters.

Tackling transmission: An important feature of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is whether or not the vaccine prevents transmission to others. In this study, Wu et al. vaccinated mice, hamsters, and cynomolgus monkeys with a SARS-CoV-2 spike protein subunit vaccine, StriFK, plus a nitrogen bisphosphonate–modified zinc-aluminum hybrid adjuvant called FH002C. The vaccine elicited antibody and cell-mediated immunity in all three models. StriFK-FH002C vaccination prevented hamsters from transmitting virus to unvaccinated, cohoused hamsters. This was associated with lower viral load in the upper respiratory tract of vaccinated hamsters after challenge. Thus, StriFK-FH002C represents an effective vaccine candidate for SARS-CoV-2. Multiple safe and effective vaccines that elicit immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are necessary to respond to the ongoing coronavirus disease 2019 (COVID-19) pandemic. Here, we developed a protein subunit vaccine composed of spike ectodomain protein (StriFK) plus a nitrogen bisphosphonate–modified zinc-aluminum hybrid adjuvant (FH002C). StriFK-FH002C generated substantially higher neutralizing antibody titers in mice, hamsters, and cynomolgus monkeys than those observed in plasma isolated from COVID-19 convalescent individuals. StriFK-FH002C also induced both T_H1- and T_H2-polarized helper T cell responses in mice. In hamsters, StriFK-FH002C immunization protected animals against SARS-CoV-2 challenge, as shown by the absence of virus-induced weight loss, fewer symptoms of disease, and reduced lung pathology. Vaccination of hamsters with StriFK-FH002C also reduced within-cage virus transmission to unvaccinated, cohoused hamsters. In summary, StriFK-FH002C represents an effective, protein subunit–based SARS-CoV-2 vaccine candidate. [ABSTRACT FROM AUTHOR]