Schools under mandatory testing can mitigate the spread of SARS-CoV-2

We use event study models based on staggered summer vacations in Germany to estimatethe effect of school reopenings after the summer of 2021 on the spread of severe acuterespiratory syndrome coronavirus 2 (SARS-CoV-2). Estimations are based on dailycounts of confirmed coronavirus infections across all 401 German counties. A centralantipandemic measure in German schools included mandatory rapid testing multipletimes per week. Our results are consistent with mandatory testing contributing to thecontainment of the viral spread. We find a short-term increase in infection rates rightafter summer breaks, indicating the uncovering of otherwise undetected (asymptomatic)cases through the testing. After a period of about 2 wk after school reopenings, thegrowth of case numbers is smaller in states that reopened schools compared with thecontrol group of states still in summer break. The results show a similar pattern for olderage groups as well, arguably as a result of detected clusters through the school testing.This means that under certain conditions, open schools can play a role in containingthe spread of the virus. Our results suggest that closing schools as a means to reduceinfections may have unintended consequences by giving up surveillance and should beconsidered only as a last resort.