Previous SARS-CoV-2 Infection Associated with an 84% Lower Risk of Virus Reinfection

A large, multicenter study published in The Lancet on April 9, 2021, found people in the United Kingdom who had previously had COVID-19 were found to have an 84% lower risk of becoming reinfected and a 93% lower risk of symptomatic infection during 7 months of follow-up.

From June 18, 2020, to Dec 31, 2020, over 30,000 participants were enrolled in the study. The median participant age in the baseline-positive cohort was about 45 years, 84.2% were women, and 87.3% were White.

The median follow-up was 275 days in the positive group and 195 days in the negative group. This time period is the minimum probable effect because seroconversions were not included, stated the researchers.

This study shows that previous infection with SARS-CoV-2 induces effective immunity to future infections in most individuals, concluded the study.

A related editorial published by The Lancet on April 9th stated, 'The authors' findings suggest that infection and the development of an antibody response provide protection similar to or even better than currently used SARS-CoV-2 vaccines.'

'Although antibodies induced by SARS-CoV-2 infection are more variable and often lower in titer than antibody responses induced after vaccination, this observation does make sense considering current SARS-CoV-2 vaccines induce systemic immune responses to spike proteins while natural infection also induces mucosal immune responses and immune responses against the many other open reading frames encoded by the approximately 29,900 nucleotides of SARS-CoV-2.

The SIREN study adds to a growing number of studies, which demonstrate that infection does protect against reinfection, and probably in an antibody-dependent manner.

The study was funded by the Department of Health and Social Care of the UK Government, Public Health England, The National Institute for Health Research, with contributions from the Scottish, Welsh and Northern Irish governments.