Summer School Holidays and the Growth Rate in SARS-CoV-2 Infections Across German Districts

Abstract

Background: The Robert-Koch-Institute reports that during the summer holiday period a foreign country is stated as the most likely place of infection for an average of 27 and a maximum of 49 percent of new Sars-CoV-2 infections in Germany. Yet, infection may have taken place elsewhere, not all international travel is holiday-related and any impact of holiday-related travel will not be restricted to holidays abroad. Methods: In Germany, summer school holidays are coordinated between states and spread out over 13 weeks. We analyse the association between these holidays and the weekly infection growth rate in SARS-CoV-2 infections across 401 German districts. Employing a dynamic model with district fixed effects, we test whether the holiday season results in a statistically significantly higher infection growth rate than the period of two weeks before holidays start, our presumed counterfactual. Findings: We find effects of the holiday period equal in size to almost 50 percent of the average district growth rate in new infections in Germany during their respective final week of holidays and the two weeks after holidays end. States in the West of Germany tend to experience stronger effects than those in the East. This is consistent with another result, namely that we find statistically significant interaction effects of school holidays with per capita taxable income and the share of foreign residents in a district’s population, with both factors hypothesised to increase holiday-related travels. Interpretation: Our results suggest that changed behaviour during the holiday season accelerated the pandemic and made it considerably more difficult for public health authorities to contain the spread of the virus by means of contact tracing. Governments did not prepare adequately or timely for this acceleration. Funding: NoneDeclaration of Interests: The authors declare no competing interests.