Antibodies to SARS-CoV-2 protect against re-infection during outbreaks in care homes, September and October 2020.

ABSTRACT

Two London care homes experienced a second COVID-19 outbreak, with 29/209 (13.9%) SARS-CoV-2 RT-PCR-positive cases (16/103 residents, 13/106 staff). In those with prior SARS-CoV-2 exposure, 1/88 (1.1%) individuals (antibody positive 87; RT-PCR-positive 1) became PCR-positive compared with 22/73 (30.1%) with confirmed seronegative status. After four months protection offered by prior infection against re-infection was 96.2% (95% confidence interval (CI) 72.7-99.5%) using risk ratios from comparison of proportions and 96.1% (95% CI 78.8-99.3%) using a penalised logistic regression model.