Sars-Cov-2 Infection And Transmission In School Settings During The Second Covid-19 Wave: A Cross-Sectional Study, Berlin, Germany, November 2020

Background: School attendance during the COVID-19 pandemic is intensely debated. Aim: In November 2020, we assessed SARS-CoV-2 infections and sero-reactivity in 24 randomly selected school classes and connected households in Berlin, Germany. Methods: We collected oro-nasopharyngeal swabs and blood samples, examining SARS-CoV-2 infection and IgG antibodies by RT-PCR and ELISA. Household members self-swabbed. We assessed individual and institu-tional prevention measures. Classes with SARS-CoV-2 infection and connected households were retested after 1 week. Results: We examined 1,119 participants, including 177 primary and 175 secondary school stu-dents, 142 staff and 625 household members. SARS-CoV-2 infection occurred in eight classes, affecting each 1-2 individuals. Infection prevalence was 2.7% (95% confidence interval (CI): 1.2-5.0; 9/338), 1.4% (95% CI: 0.2-5.1; 2/140), and 2.3% (95% CI: 1.3-3.8; 14/611) among students, staff and household mem-bers. Six of nine infected students were asympto-matic at testing. We detected IgG antibodies in 2.0% (95%CI: 0.8-4.1; 7/347), 1.4% (95% CI: 0.2-5.0; 2/141) and 1.4% (95% CI: 0.6-2.7; 8/576). Prevalence increased with inconsistent facemask-use in school, walking to school, and case-contacts outside school. For three of nine households with infection(s), origin in school seemed possible. After 1 week, no school-related secondary infections appeared in affected classes; the attack rate in connected households was 1.1%. Conclusion: School attendance under rigorously implemented preventive measures seems reasonable. Balancing risks and benefits of school closures need to consider possible spill-over infection into house-holds. Deeper insight is required into the infection risks due to being a schoolchild vs attending school.