On Friday, the Centers for Disease Control and Prevention released three studies that show that COVID-19 infections were more pervasive in areas that did not require masks in schools.
The studies provide further evidence that the CDC's recommendation that teachers, staff and students wear masks when in school significantly lessen the spread of COVID-19.
One of the studies, which was conducted in Arizona, showed that schools that did not require universal masking were 3.5 times more likely to have a COVID-19 outbreak than schools that did require masks.
A second study found that the case rates of COVID-19 among children were nearly half as low in counties that require masks in schools compared to counties that did not require masks in schools. In counties that required masks in schools, the pediatric case rate was 16.32 per 100,000, compared to 34.85 for counties that did not require masks in schools.
A third study concluded that 1,801 schools across the country have had to close at some point this school year due to COVID-19 outbreaks. The number of closures was highest in the South, where more governments have taken action to limit the use of masks in schools.
Still, the CDC said Friday that 96% of schools across the country have been able to remain open for in-person learning during the 2021-22 school year.
"These studies continue to demonstrate the importance and effectiveness of CDC's Guidance for COVID-19 Prevention in K-12 Schools to help districts ensure safer in-person learning and stop the spread of COVID-19," the agency said in a statement. "Promoting vaccination of eligible persons, mask wearing, and screening testing are all proven methods to continue to work towards the end of the COVID-19 pandemic."