SARS-CoV-2 cross-sectional seroprevalence study among public school staff in Metro Vancouver after the first Omicron wave in British Columbia, Canada

Abstract

ObjectiveTo determine the SARS-CoV-2 seroprevalence among school workers within the Greater Vancouver area, British Columbia, Canada, after the first Omicron wave.DesignCross-sectional study by online questionnaire, with blood serology testing.SettingThree main school districts (Vancouver, Richmond and Delta) in the Vancouver metropolitan area.ParticipantsActive school staff enrolled from January to April 2022, with serology testing between 27 January and 8 April 2022. Seroprevalence estimates were compared with data obtained from Canadian blood donors weighted over the same sampling period, age, sex and postal code distribution.Primary and secondary outcomesSARS-CoV-2 nucleocapsid antibody testing results adjusted for test sensitivity and specificity, and regional variation across school districts using Bayesian models.ResultsOf 1850 school staff enrolled, 65.8% (1214/1845) reported close contact with a COVID-19 case outside the household. Of those close contacts, 51.5% (625/1214) were a student and 54.9% (666/1214) were a coworker. Cumulative incidence of COVID-19 positive testing by self-reported nucleic acid or rapid antigen testing since the beginning of the pandemic was 15.8% (291/1845). In a representative sample of 1620 school staff who completed serology testing (87.6%), the adjusted seroprevalence was 26.5% (95% CrI 23.9% to 29.3%), compared with 32.4% (95% CrI 30.6% to 34.5%) among 7164 blood donors.ConclusionDespite frequent COVID-19 exposures reported, SARS-CoV-2 seroprevalence among school staff in this setting remained no greater than the community reference group. Results are consistent with the premise that many infections were acquired outside the school setting, even with Omicron.

Reduced seasonal coronavirus incidence in high‐risk population groups during the COVID‐19 pandemic

“…In contrast to our analysis, a higher risk of SARS‐CoV‐2 infection has been reported in adults living with children in the United States 34 and the United Kingdom 35 . Other studies in North America have found that SARS‐CoV‐2 infection was no greater among school staff than in the community and that most COVID‐19 cases among students and teachers were acquired outside the school environment 36–38 . One of these studies was conducted in Ontario during the first wave of the pandemic 37 .…”

“… 35 Other studies in North America have found that SARS‐CoV‐2 infection was no greater among school staff than in the community and that most COVID‐19 cases among students and teachers were acquired outside the school environment. 36 , 37 , 38 One of these studies was conducted in Ontario during the first wave of the pandemic. 37 As with our cohort, participants in this study were subject to similar community‐based nonpharmaceutical public health interventions so we believe it is appropriate to compare results between studies.…”