SARS-CoV-2 seropositivity and subsequent infection risk in healthy young adults: a prospective cohort study
Study of predominantly male US Marine recruits found those who were SARS-CoV-2 IgG seropositive had a lower risk of infection during the subsequent 6 weeks than those who were seronegative (1.1 vs 6.2 cases per person-year; incidence rate ratio 0.18; 95% CI 0.11–0.28; p<0.001).
Source:
The Lancet Respiratory Medicine
SPS commentary:
The authors note that despite seropositivity, some individuals can be re-infected with Covid-19. Their findings suggest the risk of subsequent infection in seropositive healthy young adults is about one-fifth of that in seronegative individuals, and may be associated with lower IgG antibody titres or with a failure to generate or to sustain neutralising antibodies. Despite previous infection, vaccination may still be necessary to boost the natural immune response, prevent reinfection and reduce transmission.