Education Week reported a new study that confirms the value of masking during the pandemic.

Mask requirements still offer one of the strongest tools to prevent COVID-19 outbreaks in schools, say new studies.

The findings come from the Centers for Disease Control and Prevention and from a nationwide study published this morning in the journal Pediatrics. They land as the latest pandemic wave recedes, federal masking guidelines begin to relax, and education leaders work toward more flexible approaches to masking for staff and students.

In the Pediatrics study, Duke University researchers in the ongoing ABC Science Collaborative—which tracks pandemic mitigation efforts in schools—analyzed masking policies and infection rates in 61 districts, more than 3,000 schools, and more than 1.1 million students and adults in nine states. For the first time, the national study looked at mitigation from July through December 2021, during the delta wave and the start of the omicron waves of the pandemic.

Schools that required universal masking for adults and students saw 72 percent fewer secondary infections—in which students infected with COVID-19 in the community spread the virus to others in school—than did schools that had no mask requirements or partial masking. Once school size, vaccination rates, and other characteristics were taken into account, schools with universal masking had nearly 90 percent lower infection rates.

Moreover, about half of the students and staff in the study had completed vaccination against COVID-19 by the end of the study, and Duke researchers found universal masking policies were associated with fewer infections even among those who were already vaccinated.

As of March 7, just over 26 percent of U.S. children ages 5 to 11 have been fully vaccinated, as have less than 58 percent of those ages 12 to 17, according to the latest CDC data.