Seroprevalence of SARS-CoV-2 among health care workers in 10 hospitals in Quebec, Canada: a cross-sectional study

Background: The SARS-CoV-19 pandemic disproportionately affected health care workers. We aimed to measure SARS-CoV-2 seroprevalence among healthcare workers in hospitals in Quebec, Canada, after the first wave of the pandemic to explore factors associated with SARS-CoV-2-seropositivity. Methods: Between July 6 and September 24, 2020, we recruited HCWs from 10 hospitals, 8 of which were from a region with a high incidence of COVID-19 (Montreal area) and 2 from regions of Quebec with a low incidence. Eligible healthcare workers were physicians, nurses, orderlies, and housekeepers working in 4 types of care units (emergency, intensive care, COVID-19 hospital unit, and non-COVID-19 hospital unit). Participants completed a questionnaire and underwent serological screening for SARS-CoV-2. We identified factors that were independently associated with higher seroprevalence. Results: Of the 2056 HCWs recruited, 241 (11.7%) were found to be SARS-CoV-2-positive. Of these, 171 (71.0%) had a prior diagnosis of COVID-19. Seroprevalence varied among hospitals, from 2.4% to 3.7% in areas with low incidence to 17.9%-32.0% in hospitals with outbreaks involving 5 or more HCWs. Higher seroprevalence was associated with working in a hospital with outbreaks (adjusted prevalence ratio 4.16, 95% confidence interval [CI] 2.63-6.57), being a nurse or nursing assistant (adjusted prevalence ratio 1, 34, 95% CI 1.03-1.74), orderly (adjusted prevalence ratio 1.49, 95% CI 1.12-1.97), and black or Hispanic ethnicity (adjusted prevalence ratio 1.41, 95% CI 1.13-1.76). Lower seroprevalence was associated with working in an intensive care unit (adjusted prevalence ratio 0.47, 95% CI 0.30-0.71) or emergency department (adjusted prevalence ratio 0.61, 95% CI 0.39-0.98). Interpretation: Healthcare workers in Quebec hospitals have been exposed to a high risk of SARS-CoV-2 infection, particularly during outbreaks. Work is needed to better understand the dynamics of SARS-CoV-2 transmission in healthcare settings.