First direct evidence: SARS-CoV-2 neutralizing antibodies protect against re-infection in humans
Vaccine development against SARS-CoV-2 would be greatly facilitated by the identification of immunological parameters that correlate with protection in humans. However, to date, most studies on protective immunity have only been performed in animal models and correlates of protection have not been established in humans. This study provides the first direct evidence that SARS-CoV-2 neutralizing antibodies protect against SARS-CoV-2 re-infection in humans.
This new study (MedRxiv, 13 Aug 2020) done by Greninger lab at the University of Washington School of Medicine in Seattle describes a SARS-CoV-2 outbreak reported on a fishing vessel that was associated with a high attack rate (>85%).
122 sailors went on a ship, out of which 6 had anti-SARS-CoV-2 antibodies prior to starting the trip. Only three crew-members tested seropositive prior to the boat's departure in initial serological screening and also had neutralizing and spike-reactive antibodies in follow-up assays. Then 104 people out of 122 got infected on the ship. Metagenomic sequencing of 39 viral genomes suggested the outbreak originated largely from a single viral clade.
However, the 3 crew members with prior neutralising antibodies did not become PCR positive. None of these 3 crew-members with neutralizing antibody titers showed evidence of any bona fide viral infection or experienced any symptoms during the viral outbreak. Therefore, the authors conclude that the presence of neutralizing antibodies from a prior infection was significantly associated with protection against re-infection.
The study, a non-peer-reviewed preprint has several limitations (can be read in full article), but even with such a high attack rate (>85%), the lack of infection in those three crew- members with neutralizing antibodies was statistically significant in comparison the rest of the boat’s crew.
Overall, the study provides the first direct evidence that anti-SARS-CoV-2 neutralizing antibodies are protective against SARS-CoV-2 infection in humans. This evidence is encouraging as we wait for more studies.