SARS‑CoV‑2 incidence in secondary schools: the role of national and school‑initiated COVID‑19 measures

Lotte Jonker, Kimberly J. Linde, Annemarijn R. de Boer*, Er Ding, D. Zhang, M.L.A. de Hoog, Sander Herfst, Dick Heederik, P.M. Bluyssen, More Authors

*Corresponding author for this work

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1 Citation (Scopus)
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Abstract

Introduction: Our aim was to gain insight into the effect of COVID-19 measures on SARS-CoV-2 incidence in secondary schools and the association with classroom CO 2 concentration and airborne contamination. Methods: Between October 2020—June 2021, 18 schools weekly reported SARS-CoV-2 incidence and completed surveys on school-initiated COVID-19 measures (e.g. improving hygiene or minimizing contacts). CO 2 was measured in occupied classrooms twice, and SARS-CoV-2 air contamination longitudinally using electrostatic dust collectors (EDC) and analyzed using RT-qPCR. National COVID-19 policy measures varied during pre-lockdown, lockdown and post-lockdown periods. During the entire study, schools were recommended to improve ventilation. SARS-CoV-2 incidence rate ratios (IRR) were estimated by Generalized Estimating Equation (GEE) models. Results: During 18 weeks follow-up (range: 10–22) SARS-CoV-2 school-incidence decreased during national lockdown (adjusted IRR: 0.41, 95%CI: 0.21–0.80) and post-lockdown (IRR: 0.60, 0.39–0.93) compared to pre-lockdown. School-initiated COVID-19 measures had no additional effect. Pre-lockdown, IRRs per 10% increase in time CO 2 exceeded 400, 550 and 800 ppm above outdoor level respectively, were 1.08 (1.00–1.16), 1.10 (1.02–1.19), and 1.08 (0.95–1.22). Post-lockdown, CO 2-concentrations were considerably lower and not associated with SARS-CoV-2 incidence. No SARS-CoV-2 RNA was detected in any of the EDC samples. Conclusion: During a period with low SARS-CoV-2 population immunity and increased attention to ventilation, with CO 2 levels most of the time below acceptable thresholds, only the national policy during and post-lockdown of reduced class-occupancy, stringent quarantine, and contact testing reduced SARS-CoV-2 incidence in Dutch secondary schools. Widespread SARS-CoV-2 air contamination could not be demonstrated in schools under the prevailing conditions during the study.

Original languageEnglish
Article number1243
Number of pages12
JournalBMC Public Health
Volume23
Issue number1
DOIs
Publication statusPublished - 2023

Keywords

  • SARS-CoV-2
  • COVID-19 measures
  • Secondary schools
  • Air contamination
  • CO2 concentration

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