Immune correlates of protection by mRNA-1273 vaccine against SARS-CoV-2 in nonhuman primates

Immune correlates of protection can be used as surrogate endpoints for vaccine efficacy. Here, nonhuman primates (NHPs) received either no vaccine or doses ranging from 0.3 to 100 mg of the mRNA-1273 severe acute respiratory syndrome coronavirus 2 ( SARS-CoV-2) vaccine. mRNA-1273 vaccination elicited circulating and mucosal antibody responses in a dose-dependent manner. Viral replication was significantly reduced in bronchoalveolar lavages and nasal swabs after SARS-CoV-2 challenge in vaccinated animals and most strongly correlated with levels of anti-S antibody and neutralizing activity. Lower antibody levels were needed for reduction of viral replication in the lower airway than in the upper airway. Passive transfer of mRNA-1273-induced immunoglobulin G to naive hamsters was sufficient to mediate protection. Thus, mRNA-1273 vaccine-induced humoral immune responses are a mechanistic correlate of protection against SARS-CoV-2 in NHPs.

Automated summary

In nonhuman primates (NHPs), vaccination with mRNA-1273 induces dose-dependent antibody responses, leading to a significant reduction in viral replication post SARS-CoV-2 challenge. Replication of the virus correlates strongly with antibody levels and neutralizing activity, with lower levels required in the lower airway than in the upper airway. Passive transfer of mRNA-1273-induced IgG is sufficient to provide protection, indicating that humoral immune responses induced by mRNA-1273 vaccine are effective against SARS-CoV-2 in NHPs.