ATLANTA — The Centers for Disease Control and Prevention released two studies on Friday which the agency said showed higher case circulation of COVID-19 in areas that did not have school masking policies.
The studies were released in the CDC's Morbidity and Mortality Weekly Report, and looked at one report on the two most populous counties in Arizona and another study that looked at how case rates changed following the first two weeks of school.
The research, the CDC said in a release, "found that school districts without a universal masking policy in place were more likely to have COVID-19 outbreaks."
The first study, looking at Maricopa County and Pima County in Arizona, found that 24% of schools with no mask requirement experienced an outbreak in July or August, 2021, while 20% of schools that instituted a mask requirement late (any time after the start of the school year) also saw an outbreak.
Of schools that had an early mask requirement (one in place when the year began), just 8% saw an outbreak.
"In the crude analysis, the odds of a school-associated COVID-19 outbreak in schools with no mask requirement were 3.7 times higher than those in schools with an early mask requirement," the authors of the Arizona study wrote.
The second study looked at COVID circulation in various districts around the country, and measured how case rates changed after the school year.
That study found that while counties both with and without mask requirements saw COVID spikes once the school year started, counties without mask mandates saw roughly 18.5 more new cases per 100,000 residents following the return of school than counties that had school mask mandates.
The second study's findings were subject to some limitations outlined by its authors, including that "because of the small sample size of counties selected for the analysis, the findings might not be generalizable." It also did not control for teacher vaccination rate.
The research, the CDC said, "highlight(s) the importance of using layered prevention strategies including universal masking to stop the spread and minimize disruptions to school operations for safe in-person education."