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.

Automated summary

The study found that during the COVID-19 pandemic, the infection rate of SARS-CoV-2 in schools was relatively low, but there were cases of infection in individual classes and households. Infections among students may be related to inconsistent facemask use, walking to school, and contacts outside of school.