197 of 3056 staff (6.4% [95% CI, 5.5%-7.3%]) had IgG antibodies for SARS-CoV-2.

Age and sex were not statistically significantly different among staff with or without antibodies (mean age, 39.5 [SD, 13.1] vs 41.3 [SD, 12.4] years; 38/197 [19%] vs 614/2859 [21%] men). Being involved in clinical care, having worked during the lockdown phase, being involved in care for patients with COVID-19, and exposure to COVID-19–positive coworkers were not statistically significantly associated with seroprevalence.

Having a household contact with suspected or confirmed COVID-19 was associated with antibody positivity (81/593 [13.7%] with household contacts vs 116/2435 [4.8%] without household exposure; P < .001), with an odds ratio of 3.15 (95% CI, 2.33-4.25).

A high proportion of staff mentioned at least 1 prior symptom (2294/3052 [75%]). Of those with antibodies, 30 of 197 (15%) reported no symptoms. Prior anosmia was associated with the presence of antibodies, with an odds ratio of 7.78 (95% CI, 5.22-11.53), as well as fever and cough.