High anti-SARS-CoV-2 antibody seroprevalence in healthcare workers in an Irish university teaching hospital

Introduction Healthcare workers are at very high risk for SARS-CoV-2 exposure and infection. This study evaluated anti-SARS-CoV-2 seroprevalence in healthcare workers in a tertiary care hospital and then correlated seroprevalence with confirmed or suspected SARS-CoV-2 infection in this population since the onset of the COVID-19 pandemic. Method The study was approved by our institution’s Joint Research Ethics Committee in June 2020. All volunteers were provided with a consent form, an information leaflet and a questionnaire on the day before phlebotomy. Serum samples were collected from 1176 participants over a 3-month period and analysed using the Elecsys Anti-SARS-CoV-2 assay (Roche Diagnostics GmbH, Mannheim, Germany) which detects total antibodies against the nucleocapsid protein of SARs-COV-2. Results Overall anti-SARS-CoV-2 seroprevalence among participating healthcare workers was 17.9%. The rate of confirmed infection by real-time polymerase chain reaction molecular testing prior to participation was 12.2%. Of 211 participants who had a reactive antibody test result, 37% did not have COVID-19 infection confirmed at any point prior to participation in this study, either having had a swab which did not detect SARS-CoV-2 RNA or having never been tested. Seropositivity was the highest (30%) in the youngest quintile of age (20–29 years old). Staff with more patient contact had a higher seroprevalence of 19.5% compared to 13.4% in staff with less patient contact. Conclusion This study demonstrates that a substantial proportion of SARS-CoV-2 infections in healthcare workers may be asymptomatic or subclinical and thus potentially represent a significant transmission risk to colleagues and patients.