SARS-CoV-2 seroprevalence in children, parents and school personnel from June 2020 to April 2021: cohort study of 55 schools in Switzerland

We measured SARS-CoV-2 seroprevalence in cohorts of children, parents and school personnel in 55 randomly selected schools in the canton of Zurich, Switzerland. In June-September 2020, seroprevalence was low (4.4% to 5.8%) in all cohorts. In March-April 2021, seroprevalence in children and parents (18.1% and 20.9%) was slightly higher than in school personnel (16.9%). Children’s seroprevalence was slightly higher in classes with infected main teachers and families with one infected parent, and substantially higher in families with two infected parents.