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We use event study models based on staggered summer vacations in Germany to estimate the effect of school reopenings after the summer of 2021 on the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Estimations are based on daily counts of confirmed coronavirus infections across all 401 German counties. A central antipandemic measure in German schools included mandatory rapid testing multiple times per week. Our results are consistent with mandatory testing contributing to the containment of the viral spread. We find a short-term increase in infection rates right after summer breaks, indicating the uncovering of otherwise undetected (asymptomatic) cases through the testing. After a period of about 2 wk after school reopenings, the growth of case numbers is smaller in states that reopened schools compared with the control group of states still in summer break. The results show a similar pattern for older age 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 containing the spread of the virus. Our results suggest that closing schools as a means to reduce infections may have unintended consequences by giving up surveillance and should be considered only as a last resort.

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Background Various forms of contact restrictions have been adopted in response to the Covid-19 pandemic. Around February 2021, rapid testing appeared as a new policy instrument. Some claim it may serve as a substitute for contact restrictions. We study the strength of this argument by evaluating the effects of a unique policy experiment: In March and April 2021, the city of Tübingen set up a testing scheme while relaxing contact restrictions. Methods We compare case rates in Tübingen county to an appropriately identified control unit. We employ the synthetic control method. We base interpretations of our findings on an extended SEIR model. Findings The experiment led to an increase in the reported case rate. This increase is robust across alternative statistical specifications. This is also due to more testing leading initially to more reported cases. An epidemiological model that corrects for ‘more cases due to more testing’ and ‘reduced testing and reporting during the Easter holiday’ confirms that the overall effect of the experiment led to more infections. Interpretation The number of rapid tests were not sufficiently high in this experiment to compensate for more contacts and thereby infections caused by relaxing contact restrictions.

Various forms of contact restriction have been adopted in response to the Covid-19 pandemic. Only recently, rapid testing appeared as a new policy instrument. If sufficiently effective, it may serve as a substitute for contact restrictions. Against this background we evaluate the effects of a unique policy experiment: on March 16, the city of Tuebingen set up a rapid testing scheme while relaxing lockdown measures-in sharp contrast to its German peers. Comparing case rates in Tuebingen county to an appropriately defined control unit over a four-week period, we find an increase in the reported case rate, robustly across alternative specifications. However, the increase is temporary and about one half of it reflects cases that would have gone undetected in the absence of extra testing.

The city of Augustusburg allowed for opening of, inter alia, restaurants and hotels joint with large-scale testing. We evaluate this testing & opening (T&O) experiment by comparing the evolution of case rates in Augustusburg with the evolution in other communities of Saxony. We have access to small-scale SARS-CoV-2 infection data at the community level (Gemeinde) instead of the county level (Landkreis) usually used for disease surveillance. Despite data challenges, we conclude that T&O did not lead to any increase in case rates in Augustusburg compared to its control county. When we measure the effect of T&O on cumulative cases, we find a small increase in Augustusburg. This difference almost completely disappears when we control for the effect of higher case rates due to more testing. Generally speaking, T&O worked much better than in comparable projects elsewhere.

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