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.
Another study from the CDC looked at the impact of school mask mandates across the U.S.
Authors looked at data from 520 counties that started school between July 1 and September 4 this year and had at least a full week of case data from the school year. They only looked at counties where all the schools had the same mask policies. Of the 520 counties, 198 had a school mask requirement and 322 did not.
Researchers found that counties that had no mask requirements in their schools had a higher rate of pediatric COVID cases after the school year began than those schools that did have requirements. Schools that required masks, the study found, had 16.32 cases per 100,000 children in the first week of classes; schools without had 34.85 cases per 100,000 children.
Authors did note, however, that all children in the counties were included in the data and not just those who are school-age. They also noted that teacher vaccinate rates and school testing data were not controlled in the analyses, and that the sample size of counties is small.
In both studies, authors reiterated that "consistent and correct mask use is a critical strategy" for preventing the spread of COVID-19.
Teenagers have recently made up the majority of weekly cases, according to the CDC, with elderly adults making up some of the lowest numbers of weekly cases.
The new research comes amid ongoing debates over mask mandates — a hot-button issue in some parts of the country.
Several states, including Florida, Texas and Arizona, have attempted to ban school districts from enforcing masks. Meanwhile, schools in Iowa, South Carolina, Tennessee are undergoing investigations from the Department of Education for their mask mandate bans, with the department saying the decision can put students' health in jeopardy.
School board meetings have become a focal point for mask mandate debates. With many districts weighing their options for new rules to curb the spread of COVID-19, many have jumped in to claim that requiring masks is not necessary and a violation of their rights.
A CBS News poll in August found that while more than half of surveyed parents believe schools should require masks for children, 36% believe they should be optional, and 6% think they shouldn't be allowed at all. Additionally, 52% of surveyed parents think vaccines should not be required for students.
The CDC has maintained that universal indoor masking is an important tool in helping prevent the spread. The agency says all teachers, staff, students and visitors in K-12 schools should wear masks, regardless of their vaccination status.
First published on September 25, 2021 / 11:35 AM
© 2021 CBS Interactive Inc. All Rights Reserved.