CDC: Schools Without Mask Rules Have More COVID Cases

Ralph Ellis

September 27, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Schools that didn't have masking requirements at the start of the school year reported far more COVID-19 cases and outbreaks than schools that did have mask rules, according to studies released Friday by the U.S. Centers for Disease Control and Prevention.

One study conducted in Arizona found that schools without mask rules were 3.5 times as likely to have a coronavirus outbreak than schools with those rules.

Researchers examined data from 1,020 K-12 schools in Maricopa and Pima Counties, where the majority of Arizona's population lives, from July 15-August 31. School started in July there.

A total of 191 outbreaks occurred -- 113 (59.2%) in schools without mask requirements, 16 (8.4%) in schools that had mask requirements when classes started, and 62 (32.5%) in schools that decided to require masks after the start of the school year.

The CDC defined a school-associated outbreak as occurring when two or more laboratory-confirmed cases occurred among students or staff within a 14-day period after the start of school. A school was considered to have a mask requirement when everybody was required to wear a mask indoors in school, regardless of vaccination status.

A second study found that counties without school masking rules reported much higher increases in overall pediatric COVID cases than counties that had such rules.

Researchers looked at data from 520 counties gathered between the week before school started and the second week of school. The number of pediatric infections went up by 35 per 100,000 population in counties without mask requirements and 16 per 100,000 in counties that had mask rules.

So far this school year, about 1,800 schools have had to close because of COVID-19 outbreaks, affecting 933,000 students, the CDC said in a third report issued Friday.

"To prevent COVID-19 outbreaks in schools, CDC recommends multicomponent prevention strategies, including vaccination, universal indoor masking, screening testing, and physical distancing," the CDC said.


CDC. "Association Between K–12 School Mask Policies and School-Associated COVID-19 Outbreaks — Maricopa and Pima Counties, Arizona, July–August 2021"

CDC. "Pediatric COVID-19 Cases in Counties With and Without School Mask Requirements — United States, July 1–September 4, 2021"

CDC. "COVID-19–Related School Closures and Learning Modality Changes — United States, August 1–September 17, 2021"


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.