The re-opening of schools in Germany in late summer 2020 did not propel infections with the novel
Sars-CoV-2 virus, according to a recently published study.
„We do not find any evidence for a positive effect of the end of summer breaks on the number of
confirmed cases“, the researchers from the Institute for Labor Economics (IZA) and the University of
Bonn concluded.
School closures have been among the most common non-pharmaceutical interventions to slowdown
the spread of Covid-19. They affected more than 60 percent of the world’s student population, according
to UNESCO estimates.
At the same time, the heated debate around pros and cons of closures „is characterised by the lack of
empirical evidence on how school re-openings affect the spread of the novel coronavirus“, the authors
said. School re-openings “have not necessarily been the flip side of school closures during exponential
growth of case numbers in the first wave.”
The study tries to narrow the evidence gap and focused on the phase of full school-openings in all
German states between early August and mid-September last year, based on data by the country’s
main public health institute, the Robert-Koch-Institute (RKI).
Due to the staggered summer holidays in the federal states, the researchers were able to estimate
the impact of school openings on SARS-CoV-2 case numbers. To do this, they compared the daily
difference in case numbers between counties in federal states still on holiday and those in which the
school year had started.
The surprising results can be explained by two factors, authors Ingo Isphording, Marc Lipfert and Nico
Pestel said. First, re-opening schools under strict hygiene measures combined with quarantine
measures moved students into a controlled environment for a large part of normal workdays.
Second, school re-openings compelled parents to be more careful in avoiding any infections among
their kids, as students with Corona-related symptoms were banned from school until negatively tested.
Those changes were also substantiated by an analysis of ‚Google trends‘ internet search frequencies.
„Searches for children’s symptoms and school hygiene measures are pacing up three weeks before
school re-openings and remain constant thereafter“, according to the paper.
The authors acknowledge two caveats of the analysis: On the one hand, the rising number of new
infections in the overall population may also increase the risk of more cases among students.
On the other hand, weather conditions after school re-openings in August and September last year
were favourable for outdoor activities and ventilation of classrooms, reducing the infection threat,
while worse weather conditions in fall and winter could facilitate outbreaks in schools.
Still, the study should be taken seriously by decision-makers when considering the re-opening of
schools, given high human capital costs of school closures. The outcome of the study “stands in stark
contrast to concerns about hotspots (...) in schools which dominate debates about school re-openings
worldwide”, the authors argued.
Ingo Isphording is member of the Collaborative Research Center Transregio 224 EPoS. The presented discussion
paper is a publication without peer review of the Collaborative Research Center Transregio 224 EPoS.