Opening Schools and Trends in SARS-CoV-2 Transmission in European Countries

Objectives: Benefits of school attendance have been debated against SARS-CoV-2 contagion risks. This study examined the trends of contagion before and after schools reopened across 26 countries in the European Union. Methods: We compared the average values of estimated R ( t ) before and after school reopening, identifying any significant increase with a one-sample t-test. A meta-analysis and meta-regression analysis were performed to calculate the overall increase in R ( t ) for countries in the EU and to search for relationships between R ( t ) before schools reopened and the average increase in R ( t ) afterward. Results: The mean reproduction number increased in 16 out of 26 countries. The maximum increase in R ( t ) was reached after a mean 28 days. We found a negative relationship between the R ( t ) before school reopening and its increasing after that event. By 45 days after the first day of school reopening, the overall average increase in R ( t ) for the European Union was 23%. Conclusion: We observed a significant increase in the mean reproduction number in most European countries, a public health issue that needs strategies to contain the spread of COVID-19.