A study by Kizzmekia Corbett et al. reports that antibody responses induced by the mRNA-1273 (Moderna) vaccine are a correlate of protection against SARS-CoV-2 infection in non-human primates. Defining immune correlates of protection is a critical aspect of vaccine development for extending the use of approved vaccines and facilitating the development of new candidate vaccines. Although immune responses associated with protection after primary infection have been assessed in non-human primates (NHPs), there are no studies to date that have specifically defined immune correlates of protection in upper and lower airways after vaccination with any COVID-19 vaccine approved for use in humans. To investigate the correlates of protection for such a vaccine, Kizzmekia Corbett et al. studied NHP immune responses to various doses of the mRNA-1273 vaccine. Using bronchoalveolar lavages and nasal washes, they determined that mRNA-1273 vaccination elicited spike protein-specific antibodies in the airways, which correlated with protection against SARS-CoV-2 replication in the lungs. Lower antibody levels were needed for reduction of viral replication in the lower airway than in the upper airway, the authors found, which may explain why the current crop of vaccines is more effective against severe lower tract disease. To determine if the antibodies generated from the vaccine are not only a correlate of protection but also the mechanism of protection, the researchers transferred NHP antibodies to Syrian hamsters and found they offered protection against SARS-CoV-2 challenge. The authors note that ongoing NHP studies will assess the durability of mRNA-1273-elicited protection against global SARS-CoV-2 variants.
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Science
Immune Correlates of Protection by mRNA-1273 against SARS-CoV-2 in Nonhuman Primates
29-Jul-2021