SARS-CoV-2 Seroprevalence in Employees of Four Essential Non-Health Care Sectors at Moderate/High Risk of Exposure to Coronavirus Infection: Data From the "First Wave".

OBJECTIVE: The aim of this study was to evaluate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence in Swiss non-health care employees at a moderate to high risk of exposure: bus drivers and supermarket, laundry service, and mail-sorting center employees. METHODS: Data on 455 essential workers included demographics, SARS-CoV-2 exposure and use of protective measures. Anti-SARS-CoV-2 immunoglobulins G and A targeting the spike protein were measured between May and July 2020. RESULTS: The overall crude seroprevalence estimate (15.9%; 95% confidence interval [CI], 12.6% to 19.7%) among essential workers was not significantly higher than that of the general working-age population (11.2%; 95% CI, 7.1% to 15.2%). Seroprevalence ranged from 11.9% (95% CI, 6.3% to 19.8%) among bus drivers to 22.0% (95% CI, 12.6% to 19.7%) among food supermarket employees. CONCLUSIONS: We found no significant difference in seroprevalence between our sample of essential workers and local working-age population during the first lockdown phase of the COVID-19 pandemic. Having a seropositive housemate was the strongest predictor of SARS-CoV-2 seropositivity.