Social network-based strategies for classroom size reduction can help limit outbreaks of SARS-CoV-2 in high schools. A simulation study in classrooms of four European countries

Dividing classrooms may reduce the risk of SARS-CoV-2 outbreaks in schools. We investigate how classroom cohorting strategies, which downsize and isolate groups, may curb the spread of SARS-CoV-2. Using agent-based modelling based on a rich multi-country network dataset comprising 507 classrooms and 12,291 students, we assess random cohorting and three network-based strategies that consider students’ out-of-school contacts with classmates. Investigating effects on the number of cross-cohort transmissions, overall infections, and quarantines, our findings suggest that all cohorting strategies help to contain outbreaks, but that minimizing out-of-school contact between cohorts is most effective. Since this strategy may be hard to implement in practice, we show that a network chain nomination procedure and splitting classes by gender, both of which are easier to realize, also outperform random cohorting considerably. For all cohorting strategies, we find that rota-systems with instruction in alternating weeks contain outbreaks more effectively than same-day in-person instruction.