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Recognizing the immune correlates of protection against SARS-CoV-2 infection is a key goal in surmounting the COVID-19 pandemic. One approach is to examine levels of neutralizing antibody titers with in vitro assays after vaccination or natural infection.
Using data from seven phase 3 vaccine studies and one convalescent study, investigators normalized neutralization titers to the mean convalescent titer across all studies. Compared with the protective efficacy reported in these studies, a highly significant correlation between normalized convalescent titer and vaccine efficacy was found (r=0.905). In a logistic model, the neutralization level to achieve 50% protection against viral infection was 20.2% of the mean convalescent titer. To prev…