Universal masking reduces the risk of SARS-CoV-2 transmission among students, staff and families, according to a new study of more than one million students and school staff in the United States.

The study, published in the journal Pediatrics, was conducted across nine states in the US namely Wisconsin, North Carolina, Missouri, Washington, California, Tennessee, Georgia, Texas and Kansas from July 26, 2021 through Dec. 13, 2021 during the delta-drive surge in cases. More than 1.1 million students and 157,069 staff attending in-person school were included in the study. A total of 40,601 primary infections (acquired in the community) and 3085 secondary infections (acquired in the school) were recorded.

All the school districts had different masking policies. Masking was optional in six out of the 61 school districts, whereas masking was partially required in nine districts. In the rest of the 46 districts, masking was mandated inside schools for the entire duration of the study.

School districts with universal masking policy reported around 7.3 school acquired infections for every 100 community-acquired (primary) cases. For the same number of community-acquired cases, 26.4 school-associated cases (secondary) were reported in districts where masking was optional and 11.0 secondary cases in districts with partial masking. Compared to schools with compulsory masking, schools with optional masking had 3.6 times higher rate of secondary infections. School-associated infections reduced by 72% in schools with mandatory masking vis-à-vis optional masking.

Compared to optional masking, universal masking decreased school-associated infections. This finding assumes particular importance as now schools have reopened across the country. This study was conducted before the omicron wave, but it re-emphasizes the protective effects of masking in preventing infections from highly transmissible variants like Omicron, particularly in areas with high infection rates. The findings will also come to the aid of authorities in deciding about in-school mitigation measures.

Reference

1. Boutzoukas AE et al. School masking policies and secondary SARS-CoV-2 transmission. Pediatrics. 2022 Mar 9. doi: 10.1542/peds.2022-056687.