We analyzed 221 coronavirus disease 2019 cases identified between June 2020 and January 2021 in 6074 individuals screened for immunoglobulin G antibodies in May 2020, representing 77% of residents of 5 Italian municipalities. The relative risk of developing symptomatic infection in seropositive participants was 0.055 (95% confidence interval, .014-.220).
Keywords: COVID-19; SARS-CoV-2; natural immunity; reinfection risk; serological screening.
© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.