Schools move away from masks as studies suggest they are effective

Students last year at Hopkinton High School.David L. Ryan/Globe Staff

Heading into a third fall of living with COVID-19, many schools and colleges are ditching mask mandates and telling students that face coverings are optional.

The Massachusetts Department of Elementary and Secondary Education on Monday made it official, releasing fall guidelines that informed families “there is no longer any statewide masking mandate in schools (other than school health offices) and there is no testing requirement for schools.”

Some criticized the new state guidelines for failing to anticipate COVID surges and ignoring the needs of students who are immunocompromised or have other conditions that put them at high risk of severe disease.

Yet amid the relentless policy debates, infectious disease experts say one thing is clear: masks in classrooms are effective at tamping down infections.

“The best available science on masks is, if you are wearing a high-performance mask, like a KN95, it is very effective in protecting the wearer and protecting others,” said Linsey Marr, professor of civil and environmental engineering at Virginia Tech, who studies transmission of infectious disease via aerosols.

Two recent studies from different teams of Boston scientists appear to underscore the efficacy of universal masking in schools at certain times.

A study published earlier this month in JAMA Network Open from a team at Boston University found that in-class transmission of COVID was “negligible” when mandatory masking and vaccination were in place. The scientists studied reported infections among 33,000 students across 140,000 class meetings at BU from last fall’s semester, with contact tracing, weekly surveillance testing, and genomic sequencing (analyzing the DNA) of positive cases.

Scientists not involved with the study commended its rigorous approach but said because it included a population that was required to also be vaccinated, and occurred largely before Omicron appeared in late November, it is hard to tease out the specific role masks may have played then, or now.

“There is no perfect, silver bullet when it comes to studying this topic,” said John Brownstein, chief innovation officer at Boston Children’s Hospital and a professor of infectious disease epidemiology at Harvard Medical School.

Another study posted online last week, but not yet published in a peer-reviewed journal, tracked 72 Greater Boston school districts after the state lifted mandatory masking last February. The scientists measured weekly COVID cases among staff and students in districts that lifted the requirement and those that didn’t through the end of the semester.

They found that the Boston and Chelsea districts, which were the only ones that stuck with mandatory masks through June, reported among the lowest rates of new infections compared with wealthier communities that lifted their mask rules in February. The scientists noted that Boston and Chelsea, with higher concentrations of low-income families and communities of color, had experienced among the highest rates of infections and deaths earlier in the pandemic but had comparable infection rates to other communities in the weeks before the state lifted the mask mandate.

The scientists did not specifically study ventilation systems in the schools but noted that wealthier communities, with newer buildings and presumed better ventilation, still experienced higher rates of COVID after lifting mask rules.

“That was surprising to me,” said Eleanor Murray,an assistant professor of epidemiology at Boston University School of Public Health and a study coauthor.

“I was expecting that would offset any potential risk of transmission due to not masking and we wouldn’t really see that big an effect,” she said.

Murray and her colleagues recommend that school districts develop mitigation plans proactively in anticipation of a winter COVID-19 wave, requiring masks in December and January, with a clear threshold for removing masks in March or later as the winter wave abates.

Other scientists not involved in that study said several other variables outside of school may have affected the findings. They said, for instance, wealthier families may have traveled more during spring break, making them more vulnerable to infection, compared with lower-income families.

“I find the biggest challenge is, people want to say masks work, or they don’t work, that it is this black and white,” said Marr, from Virginia Tech. “The reality is, it’s somewhere in between.”

While masks help reduce transmission, they are not 100 percent effective, which is why Marr and others say a “Swiss cheese” approach of layering in other protections, including improved ventilation and boosting vaccination levels, is the most effective.

One-way masking, for students and teachers who choose to mask while many others have dropped face coverings, does confer some protection for the wearer, Marr said.

On Friday, the Centers for Disease Control and Prevention issued guidance on masking and other mitigation measures for schools that experts said was more comprehensive than what DESE released. The CDC recommended a return to “universal indoor masking” when community COVID levels are high. (None of Massachusetts’ 14 counties currently has a high community level.)

But the new state guidelines from the Department of Elementary and Secondary Education make no mention of this or several other CDC recommendations.

“The CDC guidelines were explicit that ‘Schools with students at risk for getting very sick with COVID-19 must make reasonable modifications when necessary to ensure that all students, including those with disabilities, are able to access in-person learning,’” said Dr. Jonathan Levy, who chairs the department of environmental health at BU’s School of Public Health.

The CDC guidance noted: “Schools might need to require masking in settings such as classrooms or during activities to protect students with immunocompromising conditions or other conditions that increase their risk for getting very sick with COVID-19.”

Said Levy, “DESE does not speak at all to those children and their families.”

The DESE guidelines say schools and districts may purchase masks through a state contractor, but Levy notes lack of access to affordable, high-quality masks is an urgent problem for low-income families who choose to continue masking.

“We need a radically different way to think about masks, and the way to get them into the hands of families who need them,” he said.

As Massachusetts and other states move toward individual decisions about protections, and away from universal mandates, a group of more than 75 public health, infectious disease, and education leaders from Massachusetts and across the country launched an online campaign, detailing specific mitigation plans from testing to masking for schools.

“Masking does not have to be never or always,” it said. Instead, it recommends universal masking for the first one to two weeks of the new school year, for one week after school breaks, and at the start of surges.

The plan, they said, is “intended to provide a practical approach to implementing sensible mitigation when and where it is most needed, supporting living well socially, emotionally, and physically — together in the continuing pandemic.”