Trends in Testing for SARS-CoV-2 Among Healthcare Workers in a Canadian Cohort Study During the COVID-19 Pandemic, June 2020 to November 2023

Background: While testing healthcare workers (HCWs) for SARS-CoV-2 is important to reduce transmission within healthcare settings, understanding the self-reported patterns of testing is important for interpreting vaccine effectiveness and other COVID-19-related information. Objective: Using longitudinal data from the COVID-19 Cohort Study, this study described trends in SARS-CoV-2 testing among Canadian HCWs between June 2020 and November 2023. Methods: HCWs completed an illness report for each instance of SARS-CoV-2 testing and episodes of symptoms compatible with COVID-19 even if untested. Overall rates of testing were calculated along with rates stratified by participating province, reason for testing, and COVID-19 vaccination status. Results: Rates of testing for SARS-CoV-2 generally mirrored rates of hospitalization for COVID-19 among Canadians. Rates of testing were highest during the Omicron BA.1 wave and varied by region, while vaccination status did not impact rates. The most commonly reported reason for testing was for symptoms; testing for known/possible exposure or routine reasons greatly decreased after the Omicron BA.1 wave. In participants who were tested for episodes of symptomatic illness, the mean time to first test was 1.3 days. Reported retesting after an initial negative result remained low throughout the study period. Conclusions: Understanding testing behaviours is important for public health decision-making including the analysis and interpretation of case data and vaccine effectiveness studies. It can also highlight possible missed case-finding opportunities in healthcare settings.