Opening schools and trends in SARS-CoV-2 transmission in European countries

Background: It is important to understand the role of schools in the community transmission of SARS-CoV-2, bearing in mind that children and adolescents can spread the infection within families, even when their own symptoms are mild. The aim of this study was to examine the trends of contagion before and after schools reopened across 27 countries in the European Union. Methods: All data on the number of people testing positive for COVID-19 in each European country were collected from 20 days before schools reopened to 45 days afterwards. The Joinpoint regression method was used to detect single change points on the trend of contagion. The Bayesian Information Criterion (BIC) was used for model selection purposes. Results: We calculated 27 linear regression models for the daily case numbers of SARS-CoV-2 infection in the 27 countries from 20 days before schools reopened to 45 days afterwards. A significant increase in the number of daily infections was seen for 21 countries after a change point in the linear regression lines. The change points in different countries varied, ranging from 10 to 42 days after schools reopened, with the majority occurring beyond the 21st day. Conclusion: This study analysed the trend of SARS-CoV-2 transmission before and after schools reopened in Europe. We observed a significant increase in the number of new daily cases in most countries. This issue poses a public health problem that needs to be taken into account in deciding strategies to contain the spread of COVID-19.