SARS-CoV-2 seroprevalence in students and teachers: a longitudinal study from May to October 2020 in German secondary schools

OBJECTIVE: To quantify the number of SARS-CoV-2 infections in secondary schools after their reopening in May 2020. DESIGN: Repeated SARS-CoV-2 seroprevalence study after the reopening of schools and 4 months later. SETTING: Secondary school in Dresden, Germany. PARTICIPANTS: 1538 students grades 8–12 and 507 teachers from 13 schools. INTERVENTIONS: Serial blood sampling and SARS-CoV-2 IgG antibody assessment. PRIMARY AND SECONDARY OUTCOME MEASURE: Seroprevalence of SARS-CoV-2 antibodies in study population. Number of undetected cases. RESULTS: 1538 students and 507 teachers were initially enrolled, and 1334 students and 445 teachers completed both study visits. The seroprevalence for SARS-CoV-2 antibodies was 0.6% in May/June and the same in September/October. Even in schools with reported COVID-19 cases before the lockdown of 13 March, no clusters could be identified. Of 12 persons with positive serology five had a known history of confirmed COVID-19; 23 out of 24 participants with a household history of COVID-91 were seronegative. CONCLUSIONS: Schools do not play a crucial role in driving the SARS-CoV-2 pandemic in a low-prevalence setting. Transmission in families occurs very infrequently, and the number of unreported cases is low in this age group. These observations do not support school closures as a strategy fighting the pandemic in a low-prevalence setting. TRIAL REGISTRATION NUMBER: DRKS00022455.