The Centers for Disease Control and Prevention released new studies Friday that show enforcing masks in schools helps reduce the spread of COVID-19 .
One study looked at data from schools in Arizona's Maricopa and Pima Counties after they resumed in-person learning in late July for the 2021-22 academic year. The two counties account for roughly 75% of the state's population.
The CDC found that the K-12 schools that did not have mask requirements at the beginning of the school year were 3.5 times more likely to have COVID outbreaks than schools that required all people, regardless of vaccination status, to wear a mask indoors from the first day of school.
Of the 999 schools analyzed in the study, 21% had an early mask requirement, 30.9% enacted a mask requirement between nine and 17 days after the school year began, and 48% had no mask requirement. Of the 191 COVID outbreaks that occurred in those schools from July 15 to August 31, 113 were in schools that did not enforce masks at all. Schools with early mask requirements had the lowest number of outbreaks.
During that time frame, Arizona was experiencing an upward trend of weekly COVID cases, according to Johns Hopkins University.