2024 Yes https://doi.org/10.1371/journal.pone.0305195 Gorgels, Koen M. F. Europe Observational Epidemiology Study Students Staff Elementary (K-5) Ventilation rates Viruses COVID rates Using school surveys and case registry data, this study examined the impact of ventilation systems and mask mandates on COVID-19 secondary attack rates in Dutch primary schools, finding stronger effects from ventilation compared to masking.