Immune correlates of SARS-CoV-2 protection.

The protective potential of SARS-CoV-2 neutralizing antibodies (nAbs) has not been validated in humans. This preprint study analysed an outbreak on a fishing vessel (n = 122) with an infection rate of 85%. Before departure, all individuals with available data (n = 120) were negative for SARS-CoV-2 infection by RT-PCR but 6 were positive for IgG against viral nucleoprotein. Of the 6 seropositive individuals, 3 had antibodies to SARS-CoV-2 spike protein and its receptor-binding domain (RBD) that could both neutralize pseudotyped lentiviruses and block the interaction between the RBD and the virus entry receptor ACE2. These 3 individuals did not get infected, unlike the 103 individuals who lacked pre-existing nAbs, suggesting that nAb titres are a correlate of viral immunity and, potentially, vaccine efficacy.