Immune responses associated with protection from SARS-CoV-2 infection.

Conflicting results have emerged regarding immune correlates of protection against SARS-CoV-2. In this secondary analysis of a trial of immediate versus delayed bivalent mRNA booster vaccination, we studied a range of humoral and cellular immune responses 28 days after vaccination and analyzed their association with subsequent symptomatic and asymptomatic SARS-CoV-2 infection. We found neutralizing antibodies and other plasma antibody titers correlated with prevention of SARS-CoV-2 infection. In a multivariate model, only neutralizing antibodies remained associated with protection from infection (p = 0.021). There was no significant correlation observed between B and T cell responses to Spike and protection. Our findings add to evidence of antibody correlates of prevention of SARS-CoV-2 infection. Trial registration: ANZCTR 12622000411741.