Background Reinfection after primary SARS-CoV-2 infection is uncommon in adults, but little is known about the risks, characteristics, severity or outcomes of reinfection in children. Methods We used national SARS-CoV-2 testing data in England to estimate the risk of reinfection >90 days after primary infection from 01 January 2020 to 31 July 2021, which encompassed both the Alpha and Delta waves in England. Disease severity was assessed by linking reinfection cases to national hospitalisation, intensive care admission and death registrations datasets. Findings Reinfection rates closely followed community infection rates, with a small peak during the Alpha wave and a larger peak during the Delta wave. In children aged <16 years, there were 688,418 primary infections and 2,343 reinfections. The overall reinfection rate was 66.88/100,000 population, being higher in adults (72.53/100,000) than in children (21.53/100,000). Reinfection rates after primary infection were 0.68% overall, 0.73% in adults and 0.34% in children. Of the 109 reinfections in children admitted to hospital, 78 (72%) had underlying comorbidities. Hospitalisation rates were similar for the first (64/2343, 2.73%) and second episode (57/2343, 2.43%). Intensive care admission was rare after primary infection (n=7) or reinfection (n=4), mainly in children with comorbidities. 44 deaths occurred after primary infection within 28 days of diagnosis (44/688,418, 0.01%), none after possible reinfections. Interpretation The risk of SARS-CoV-2 reinfection is strongly related to exposure due to community infection rates, especially during the Delta variant wave. Children had a lower risk of reinfection than adults, but reinfections were not associated with more severe disease or fatal outcomes. Funding PHE/UKHSA
Risk of SARS-CoV-2 reinfections in children: prospective national surveillance, January 2020 to July 2021, England