The COVID pandemic put extreme stress on the Health Care workforce. This was particularly so during the early phases of the pandemic prior to the availability of vaccines, and at which time PPE was in extreme short supply. We assessed the prevalence of antibodies to SARS COV-2 in Ontario Acute Care Health Care Workers at the after the first wave of the pandemic and found that work related factors did not predict serological evidence of exposure. Instead community exposures provided the greatest risks of seropositivity. This data was very reassuring, and suggested that existing safety precautions provided adequate protection for health care workers in the vast majority of patient interactions. This data was helpful in at least partially alleviating some of the extreme stress that health care workers were under in the workplace.

This was a prospective, multi-center study of cohort of Healthcare Workers (HCWs) in Ontario, Canada. The primary objective of this study was to assess overall seroprevalence of SARS-CoV-2 antibodies in a population of healthcare workers. Blood samples were obtained from 350 front line SARS-CoV-2 positive health care workers (HCWs) at St. Joseph’s Health Care and London Health Sciences Centre and tested for SARS-CoV-2 antibodies between May 15- Oct 7 2020 to evaluate their immune response. The study included 1062 HCWs from Ontario, 57 (5.4%) were seropositive at any time point. Seroprevalence was higher among those who had a known unprotected exposure to a patient with COVID-19 (p < 0.001) and those who had been contacted by public health because of a nonhospital exposure (p = 0.003). Providing direct care to patients with COVID-19 or working on a unit with a COVID-19 outbreak was not associated with higher seroprevalence. Health care workers exposed to household risk factors had higher SARS-CoV-2 seroprevalence than those not exposed. In multivariable logistic regression, presence of symptomatic contacts in the household was the strongest predictor of seropositivity (adjusted odds ratio 7.15, 95% confidence interval 5.42 9.41). These seropositivity results were not higher than those seen in community surveys performed at the same time. Providing direct care to patients or working on an outbreak floor were both not associated with seropositivity.
This study confirmed that routine use of PPE as carried out in Ontario Hospitals early in the pandemic did provide adequate protection of health care workers. The availability of vaccination for health care workers after this study was completed provided further levels of safety in both the community and the hospital.

SARS-CoV-2 antibodies in Ontario health care workers during and after the first wave of the pandemic: a cohort study. Michelle Science MD MSc, Shelly Bolotin PhD, Michael Silverman MD et al 2021, CMAJ OPEN, October 12, 2021 9(4) E929-E939; DOI: https://doi.org/10.9778/cmajo.20210044