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Although natural infection with COVID-19 offers some protection against reinfection, researchers are still probing just how natural immunity compares with vaccine-induced immunity and how vaccines can best be deployed to enhance natural immunity.
In a prospective U.K. study, investigators followed >35,000 asymptomatic healthcare workers (84% female; median age, 46) from December 2020 to September 2021 with biweekly SARS-CoV-2 PCR tests. About 9000 had a history of COVID-19 prior to enrollment; in this group, risk for reinfection was initially about 86% lower than among the other participants. By 1 year after infection, this reduction in risk had fallen to about 70%. With one or two subsequent immunizations (almost all with the Pfizer-BioNTec…