Seroprevalence and immunity of SARS-CoV-2 infection in children and adolescents in schools in Switzerland: design for a longitudinal, school-based prospective cohort study

Introduction

Seroprevalence and transmission routes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children and adolescents, especially in school setting, are not clear. Resulting uncertainty is reflected in very different decisions on school closures and reopenings across countries. The aim of this longitudinal cohort study is to assess the extent and patterns of seroprevalence of SARS-CoV-2 antibodies in school-attending children repeatedly. It will examine risk factors for infection, relationship between seropositivity and symptoms, and temporal persistence of antibodies. Additionally, it will include testing of school personnel and parents.

Methods and analysis

The study (Ciao Corona) will enroll a regionally representative, random sample of schools in the canton of Zurich, where 18% of the Swiss population live. Children aged 5 to 16 years, attending classes in primary and secondary schools are invited. Venous blood and saliva samples are collected for SARS-CoV-2 serological testing after the first wave of infections (June/July 2020), in fall (October/November 2020), and after winter (March/April 2021). Venous blood is also collected for serological testing of parents and school personnel. Bi-monthly questionnaires to children, parents and school personnel cover SARS-CoV-2 symptoms and tests, health, preventive behavior, lifestyle and quality of life information. Total seroprevalence and cumulative incidence will be calculated. Hierarchical Bayesian logistic regression models will account for sensitivity and specificity of the serological test in the analyses and for the complex sampling structure, i.e., clustering within classes and schools.

Ethics and dissemination

The study was approved by the Ethics Committee of the Canton of Zurich, Switzerland (2020-01336). The results of this study will be published in peer-reviewed journals and will be made available to study participants and participating schools, the Federal Office of Public Health, and the Educational Department of the canton of Zurich. Trial registration number <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="clintrialgov" xlink:href="NCT04448717">NCT04448717</ext-link> .

• Ciao Corona is a large, prospective school-based cohort study and will provide robust data on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence, transmission routes and immunity over time in a representative sample of school children.

• The longitudinal design will allow describing temporal trends of immunity to SARS-CoV-2 infection and to evaluate effects of school structure and preventive measures.

• This study will inform goal-oriented policy decisions in school management during subsequent outbreaks.

• Participation bias, missing questionnaires, desirability bias, and loss of follow up may occur. The validity of serological tests may also hamper results.