SARS-CoV-2 seroprevalence in school-children across districts, schools and classes

View ORCID ProfileAgne Ulyte, View ORCID ProfileThomas Radtke, Irene A Abela, View ORCID ProfileSarah H Haile, Jacob Blankenberger, Ruedi Jung, Celine Capelli, View ORCID ProfileChristoph Berger, View ORCID ProfileAnja Frei, View ORCID ProfileMichael Huber, Merle Schanz, Magdalena Schwarzmueller, View ORCID ProfileAlexandra Trkola, Jan Fehr, Milo A Puhan, View ORCID ProfileSusi Kriemler

doi: https://doi.org/10.1101/2020.09.18.20191254

This article is a preprint and has not been certified by peer review [what does this mean?]. It reports new medical research that has yet to be evaluated and so should not be used to guide clinical practice.

PDF: https://www.medrxiv.org/content/10.1101/2020.09.18.20191254v1.full.pdf

Abstract

Importance: Understanding transmission and impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in school children is critical to implement appropriate mitigation measures. Objective: To determine the variation in SARS-CoV-2 seroprevalence in school children across districts, schools, grades, and classes, and the relationship of SARS-CoV-2 seroprevalence with self-reported symptoms. Design: Cross-sectional analysis of baseline measurements of a longitudinal cohort study (Ciao Corona) from June-July 2020. Setting: 55 randomly selected schools and classes stratified by district in the canton of Zurich, Switzerland (1.5 million inhabitants). Participants: Children, aged 6-16 years old, attending grades 1-2, 4-5 and 7-8. Exposure: Exposure to circulating SARS-CoV-2 between February and June 2020 including public lock-down and school closure (March 16-May 10, 2020). Main Outcomes and Measures: Variation in seroprevalence of SARS-CoV-2 in children across 12 cantonal districts, schools, and grades using a Luminex-based antibody test with four targets for each of IgG, IgA and IgM. Clustering of cases within classes. Analysis of associations of seropositivity and symptoms. Comparison of seroprevalence with a randomly selected adult population, based on Luminex-based IgG and IgA antibody test of Corona Immunitas. Results: In total, 55 schools and 2585 children were recruited (1337 girls, median age 11, age range 6-16 years). Overall seroprevalence was 2.8 % (95% CI 1.6-4.1%), ranging from 1.0% to 4.5% across districts. Seroprevalence was 3.8% (1.9-6.1%) in grades 1-2, 2.5% (1.1-4.2%) in grades 4-5, and 1.5% (0.5-3.0%) in grades 7-8. At least one case was present in 36/55 tested schools and in 43/128 classes with ≥50% participation rate and ≥5 children tested. 73% of children reported COVID-19 compatible symptoms since January 2020, but none were reported more frequently in seropositive compared to seronegative children. Seroprevalence of children was very similar to seroprevalence of randomly selected adults in the same region in June-July 2020, measured with the same Corona Immunitas test, combining IgG and IgA (3.1%, 95% CI 1.4-5.4%, versus 3.3%, 95% CI 1.4-5.5%). Conclusions and Relevance: Seroprevalence was inversely related to age and revealed a dark figure of around 90 when compared to 0.03% confirmed PCR+ cases in children in the same area by end of June. We did not find clustering of SARS-CoV-2 seropositive cases in schools so far, but the follow-up of this school-based study will shed more light on transmission within and outside schools. Trial registration: ClinicalTrials.gov Identifier: NCT04448717, registered June 26, 2020. https://clinicaltrials.gov/ct2/show/NCT04448717

Competing Interest Statement

The authors have declared no competing interest.

Clinical Trial

NCT04448717

Clinical Protocols

https://www.medrxiv.org/content/10.1101/2020.08.30.20184671v1

Funding Statement

This study is part of Corona Immunitas research network, coordinated by the Swiss School of Public Health (SSPH+), and funded by fundraising of SSPH+ that includes funds of the Swiss Federal Office of Public Health and private funders (ethical guidelines for funding stated by SSPH+ will be respected), by funds of the Cantons (Vaud, Zurich and Basel) and by institutional funds of the Universities. Additional funding, specific to this study (Ciao Corona) is available from the Fondation les Murons and from the Pandemic Fund of the University of Zurich Foundation. The funder did not participate in the work.

https://www.medrxiv.org/content/10.1101/2020.09.18.20191254v1