SARS-CoV-2 seroprevalence among Vancouver public school staff in British Columbia, Canada: a cross-sectional study

  1. David M Goldfarb
  2. Louise C Mâsse
  3. Allison W Watts
  4. Sarah M Hutchison
  5. Lauren Muttucomaroe
  6. Else S Bosman
  7. Vilte E Barakauskas
  8. Alexandra Choi
  9. Nalin Dhillon
  10. Michael A Irvine
  11. Frederic Reicherz
  12. Collette O’Reilly
  13. Sadaf Sediqi
  14. Rui Yang Xu
  15. Hamid R Razzaghian
  16. Manish Sadarangani
  17. Daniel Coombs
  18. Sheila F O’Brien
  19. Pascal M Lavoie

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Abstract

Few studies reported COVID-19 cases in schools during the 2020/21 academic year in a setting of uninterrupted in-person schooling. The main objective was to determine the SARS-CoV-2 seroprevalence among school staff in Vancouver public schools.

Design

Cumulative incident COVID-19 cases among all students and school staff based on public health data, with an embedded cross-sectional serosurvey among a school staff sample that was compared to period, age, sex and geographical location-weighted data from blood donors.

Setting

Vancouver School District (British Columbia, Canada) from kindergarten to grade 12.

Participants

Active school staff enrolled from 3 February to 23 April 2021 with serology testing from 10 February to 15 May 2021.

Main outcome measures

SARS-CoV-2 seroprevalence among school staff, based on spike (S)-based (unvaccinated staff) or N-based serology testing (vaccinated staff).

Results

Public health data showed the cumulative incidence of COVID-19 among students attending in-person was 9.8 per 1000 students (n=47 280), and 13 per 1000 among school staff (n=7071). In a representative sample of 1689 school staff, 78.2% had classroom responsibilities, and spent a median of 17.6 hours in class per week (IQR: 5.0–25 hours). Although 21.5% (363/1686) of surveyed staff self-reported close contact with a COVID-19 case outside of their household (16.5% contacts were school-based), 5 cases likely acquired the infection at school based on viral testing. Sensitivity/Specificity-adjusted seroprevalence in 1556/1689 staff (92.1%) was 2.3% (95% CI: 1.6% to 3.2%), comparable to a sex, age, date and residency area-weighted seroprevalence of 2.6% (95% CI: 2.2% to 3.1%) among 5417 blood donors.

Conclusion

Seroprevalence among staff was comparable to a reference group of blood donors from the same community. These data show that in-person schooling could be safely maintained during the 2020/21 school year with mitigation measures, in a large school district in Vancouver, Canada.

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  1. Version published to 10.1136/bmjopen-2021-057846
  2. ScreenIT

    SciScore for 10.1101/2021.06.16.21258861: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsConsent: Informed consent was obtained from all school staff.
    IRB: The study was approved by the University of British Columbia Children’s and Women’s Research Ethics Board (H20-03593).
    Sex as a biological variablenot detected.
    RandomizationStatistical analyses: Blood donors were identified to match study participants by age and sex ± 2 years and two donors randomly selected without replacement for each study participant.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Antibodies directed against the spike (S1) protein were detected using the Ortho T VITROS™ Anti-SARS-CoV-2 Total antibody assay (Ortho IgG; Ortho Clinical Diagnostics, Rochester, NY), a Health Canada and FDA-licensed qualitative assay which detects all types of antibodies (IgA, IgG and IgM).
    IgA , IgG
    suggested: None
    IgM
    suggested: None
    Testing for anti-nucleocapsid (N) protein SARS-CoV-2 antibodies was performed using the Roche Elecsys™ Anti-SARS-CoV-2 (Roche T; Roche, USA).
    anti-nucleocapsid ( N ) protein SARS-CoV-2
    suggested: None
    Anti-SARS-CoV-2
    suggested: None

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    This study has limitations. First, study volunteers are typically healthier, raising a possibility that seroprevalence estimates were underestimated. To estimate this bias, the incidence of COVID-19 cases based on self-report (1.4%) was compared to the contact tracing data in classroom staff across the entire District (1.3%) and suggests that we did not under sampled those who are in direct contact with students. Second, the seroprevalence of school staff was compared to matched blood donors which may underestimate the community prevalence as the blood donors serology were taken in January 2021, prior to sampling of the school cohort, which could only reinforce our conclusions. As others have found, serologic testing in blood donors in general does reflect overall seroprevalence in the community39-42 and we would expect the seroprevalence in the reference group of blood donors for the same period to be higher, which reinforces our study conclusion. Consistent with this, seroprevalence estimates based on anonymized, residual specimens collected by the BC Centre for Disease Control in January 2021 from working age adults (attending one of ∼80 diagnostic service centres in the only outpatient laboratory network in the greater Vancouver area) ranged from 3-4% (DM Skowronski, personal communication). Second, the study had limited power to detect small differences between seroprevalence in school staff and the community. However, it is unlikely that small differences would drastica...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  3. Version published to 10.1101/2021.06.16.21258861v1 on medRxiv