What does the science really say about masking?

An emergency rule issued Aug. 31 by the Montana Department of Public Health and Human Services has intensified debate over face mask requirements for public school students in recent weeks, generating contradictory claims about the science regarding mask wearing.

DPHHS’ rule states that the scientific literature on the effectiveness of masks in reducing the spread of viral infections is “not conclusive,” citing a number of sources including a New York magazine opinion article and an as-yet-not-peer-reviewed study. The Montana Nurses Association responded last week with a memo denouncing the rule as promoting “junk science.”

Several of the sources cited by DPHHS were also quoted in a 13-page research report prepared by Gov. Greg Gianforte’s office and released to the press the same day Gianforte announced the emergency rule. The report was titled “How can you ‘follow the science’ when there is ‘no science behind mask mandates for children’?”, and claims the Centers for Disease Control’s universal masking recommendation for schools “ignores research.” 

The report draws heavily from the same New York magazine piece cited by DPHHS, as well as from tweets, media statements and a Wall Street Journal opinion article penned by half a dozen American doctors questioning evidence that masking children prevents the spread of COVID-19. It also quotes a section of a CDC report noting that transmission reduction in Georgia elementary schools with mask mandates late last year was “not statistically significant” compared to schools where masking was optional. That report subsequently stated that “universal and correct mask use is an important COVID-19 prevention strategy in schools as part of a multicomponent approach,” a conclusion not included in the governor’s office report.

As the governor’s research report indicates, some members of the medical community nationally have expressed skepticism about mandating face masks for students. The reasons underpinning those arguments vary, from potential adverse effects of long-term mask wearing to assertions of psychological and emotional impacts on school-age children. Such anti-mask positions, amplified by Gianforte and DPHHS, may support public skepticism about the efficacy of masking. But many medical experts in Montana say the appearance of debate is misleading.

“There’s no question among the medical community and major medical and public health organizations that mask wearing is one effective way of reducing the spread of the coronavirus, SARS-CoV-2,” said Lauren Wilson, pediatric hospitalist and vice president of the Montana Chapter of the American Academy of Pediatrics.

LINE OF DEFENSE

To explain how SARS-CoV-2 is transmitted from person to person, epidemiologist and infectious disease ecologist Raina Plowright pictures a room full of smokers. After each drag on their cigarettes, they exhale clouds of smoke that drift and swirl in various directions, not unlike the fine liquid droplets people expel with every breath. In the case of someone infected with the coronavirus, viral particles ride along on those droplets. Some droplets are large enough that gravity draws them to the ground quickly, she said, but others are tiny enough to remain suspended in the air.

“When you see someone smoking, you see the smoke stays in the air for some period of time,” Plowright said. “This is one of the parts of the transmission of this virus that’s really being ignored, is that so much of it’s about the air we breathe.”

Plowright is an associate professor at Montana State University’s Department of Microbiology and Immunology, and has conducted extensive research on bat-borne viruses such as SARS-CoV-2. She said there is strong observational and experimental evidence suggesting that masks are “very effective” in reducing viral disease transmission. They do so, she added, in two ways: by containing many of the droplets expelled by the wearer, and by filtering out larger droplets expelled by others. According to a lab study published last fall in the journal Aerosol Science and Technology, a cloth mask blocked, on average, 51% of respiratory droplets generated by coughing. A neck gaiter blocked 47%, or as much as 60% when doubled over. An N95 respirator blocked 99%.

Plowright acknowledges that no single intervention is 100% foolproof. Tiny droplets will still escape or intrude, particularly if masks are made of thin fabric or don’t fit well. But fewer droplets released into the air means a lower viral load, she said, and consequently a reduced likelihood of spreading COVID-19 to others.

“By wearing a mask, you are protecting those around you,” Plowright said. “You’re reducing the potential dose to all of those around you.”

Curtis Noonan, director and professor of epidemiology at the University of Montana’s School of Public and Community Health Sciences, echoes Plowright’s statement that the body of literature on masks reducing disease transmission is “pretty strong.” The literature is less robust when it comes to school settings specifically, Noonan said. But that doesn’t mean one can simply claim there’s no evidence for mask effectiveness among students.

“The evidence is in these other settings where it’s been shown — in clinical settings and population settings, community settings — that wearing masks has been effective,” Noonan said. “It’s one of many different strategies, a piece of the puzzle in terms of limiting disease transmission.”

Masks continue to be a flashpoint in the debate about how to prevent the spread of COVID-19 in public schools this fall. District-wide masking requirements in Billings and Missoula have sparked backlash from some parents. Responding to messaging from Gianforte and state Superintendent of Public Instruction Elsie Arntzen encouraging school leaders to consider “parental concerns” when weighing masking policies, School Administrators of Montana Executive Director Kirk Miller penned an op-ed last week criticizing both officials for contributing to “the unsafe feeling in our schools.” 

Regardless of the controversy around school mask mandates, former state epidemiologist Jim Murphy, who retired from DPHHS in July, sees masks continuing to play a critical role in reducing student transmission.

“Most [school-age children] will not become as ill if they get infected with COVID, but they then become able to transmit this to others in their household, some of whom may not be as lucky,” Murphy said. “With the flu we see this all the time. Schools are like little incubators where all this stuff gets passed around because you’re throwing a lot of people together in close quarters. That’s why CDC’s recommendation, as school was starting, was that schools should actively take the step and mask.”

In recent days, individual schools in Missoula, Great Falls, Bozeman, Eureka, Noxon and Fortine have announced closures or temporary transitions to remote learning due to COVID-19 outbreaks among students and staff. According to information collected and disseminated by Wilson via Twitter, none of the schools affected had mask requirements.

MISUNDERSTANDING AND MISINTERPRETATION

A common refrain among mask critics in Montana leading into the fall semester was that children exposed to the coronavirus are far less likely than adults to become sick or develop serious cases of COVID-19. Nationally, the assertion is a common enough query that the CDC includes it on its “frequently asked questions” page. And while, according to the CDC, it’s true that fewer kids than adults get sick with COVID-19, case counts and hospitalizations among youth have been rising in recent months as the more easily transmissible Delta variant continues to spread. According to the American Academy of Pediatrics, more than 243,000 COVID-19 cases were reported in children nationwide in the first week of September, the second-highest weekly count since the pandemic began.

“We know that children are at lower risk of dying than adults when they get COVID-19,” the Montana AAP’s Wilson said. “But because we’re seeing increased transmission of COVID, we’re seeing over 20% of new cases in the U.S. be among children under 18. We’re also seeing more children get sick and hospitalized.”

Wilson added that children who are hospitalized run a greater risk of developing what physicians have dubbed “long COVID.” That condition involves a long list of symptoms affecting numerous organs including the heart muscle and intestines. Long COVID can also impact the brain, she said, resulting in dizziness, difficulty concentrating and “brain fog.” 

“Ultimately,” Wilson said, “it causes a decrease in functioning such that many kids can no longer attend school or do things that they typically would be able to do.”

In addition to widespread misconceptions about the susceptibility of children to COVID-19, experts note consistent misinterpretations of what the available scientific literature actually says. One study cited by DPHHS in its emergency rule and listed by the governor’s research report is a review of past studies of mask effectiveness. While the meta-analysis was published in a peer-reviewed journal, Noonan voiced caution about inflating the relevance of the reviewed material — some of which, according to an MTFP reading, focused on the effectiveness of masks in small households rather than in large communal settings.

Another concern expressed by critics of school mask mandates is that facial coverings negatively affect the social and emotional development of children. Some evidence does suggest that prolonged mask wearing can have adverse psychological effects on children and adults. Lately, educators and psychologists have countered those arguments by highlighting a study conducted by the University of Wisconsin Madison in late 2020. That study, which was backed by grants from the National Institutes of Health, showed that 80 children ages 7 to 13 were able to correctly identify varying emotions in mask wearers as much as 28% of the time. The results prompted the authors to conclude that childrens’ ability to read and respond to emotions “may not be dramatically impaired by mask wearing during the COVID-19 pandemic.”

The study further noted that “children’s accuracy with masked facial configurations did not significantly differ from their accuracy with facial configurations that wore sunglasses — a common accessory that children encounter in their everyday lives.” 

The science is still developing around the various psychological outcomes of everyday mask use, Noonan said, “but we’re weighing the possibility of some of those consequences against the primary importance right now of preventing spread of a disease that can have an impact on some children that are not protected otherwise.”

One assertion that’s been largely debunked is that mask wearing increases the amount of carbon dioxide inhaled by the wearer. The claim is tied to a research letter published in JAMA Pediatrics in June that was retracted by the journal’s editors a month later due to “fundamental concerns about the study methodology.” It was nonetheless repeated in a Wall Street Journal opinion piece in August — the same op-ed cited by the governor’s office.

HOW SCIENCE WORKS

In many ways, the COVID-19 pandemic has broadened the scientific understanding of mask wearing. Different states and countries have implemented masking to varying degrees, affording medical experts and researchers an opportunity to observe the effects of mask use in a variety of populations in real time. Such studies are being conducted all over the globe, as they were even prior to the current crisis, and depending on how well-designed a study is, it’s findings can be applied fairly widely.

One such investigation conducted in California speaks directly to the potential impacts of mask wearing on the spread of COVID-19 in classrooms. After a May outbreak in a Marin County elementary school, a team of medical researchers mapped the spread of the virus from an unvaccinated teacher, who had worked for two days while symptomatic, to a group of 24 students. The resulting report, published by the CDC in August, revealed that of the 22 students who were tested for SARS-CoV-2, 12 received positive results. The report further noted that the teacher occasionally “read aloud unmasked to the class” despite the school’s mask mandate, and found that 80% of the students who tested positive were seated in the first two rows of the class.

Peter Chin-Hong is an infectious disease specialist and professor of medicine at the University of California San Francisco, and has worked extensively during the pandemic to improve COVID-19 safety protocols in the state’s prison system. In an interview, he pointed to the Marin County report as “really speaking to the power of masks.”

“The ventilation in that outbreak was constant, the physical distancing was constant,” Chin-Hong said. “What was only different was the teacher not wearing a mask.”

That investigation may not be scientifically conclusive on its own, but it is part of an ever-growing understanding of coronavirus transmission and the significance of masks in containing the disease. Chin-Hong rattled off a list of additional pandemic-era insights, including a study in North Carolina showing no incidence of child transmission of COVID-19 during a period of high community spread and mandatory in-school mask wearing, and another revealing only seven cases in K-12 schools in rural Wisconsin during a time when masks were required.

During a public COVID-19 update last month, Gianforte said the CDC’s guidance has been “all over the map.” Other critics of the federal government’s approach to the pandemic have similarly accused the CDC of flip-flopping, pointing to advice from U.S. health leaders early in the pandemic against mask wearing and the CDC’s recent update stating that vaccinated individuals should continue to mask indoors. 

MSU’s Plowright, however said changes in public health guidance aren’t contradictions, but rather a reflection of new discoveries about the disease.

For example, Plowright notes that in the first months of the pandemic, scientists were still observing and studying exactly how the coronavirus spread. An early theory was that viral particles survived on surfaces for extended periods of time, prompting health officials to emphasize cleaning and sanitization. Once the extent of COVID-19’s aerosolized spread was discovered, masking emerged as a primary tool in preventing transmission.

“We’re constantly learning,” Plowright said. “So if we weren’t changing our advice as we learn about this new pathogen, we’d be terrible scientists. If we came out of the beginning and said, ‘This is how it all works. That’s it. You follow that. Done,’ that would be absolutely disastrous public health advice or science. Our science is that we’re constantly exploring to get to the truth.”

Over the past year and a half, Plowright continued, she’s observed some members of the public increasingly putting stock in anecdotes, rather than in the evolving advances made by scientists. She said there’s a “fundamental lack of understanding in the community” about how science works. Studies have to be carefully designed with regard to sample size, randomization and replication in order to generate accurate and thorough results. 

To accomplish those ends, Chin-Hong said, scientists have to be “unbiased” and “agnostic,” a duty made more difficult in situations, like the current pandemic, that have become divisively politicized. The latest example, he noted, is the mixed response to President Joe Biden’s order last week requiring all companies nationwide with more than 100 workers to mandate the vaccine for employees or else conduct weekly testing. Despite heated pushback from some sectors of the American public, Chin-Hong and others interviewed for this story insisted that vaccination is still the most effective defense against the continued spread of COVID-19. Chin-Hong’s approach to informing the public about the science behind vaccination, masking and other pandemic responses is to speak plainly, listen to their concerns, and provide the best examples he can from the available scientific literature.

“But at the end of the day, I can’t convince everybody all the time,” Chin-Hong said. “And that’s why these mandates are really important, because America is all about individual rights and freedom. But when you talk about a pandemic, you leave the individual realm and you are talking about community protection.”

Chin-Hong said he’s still “baffled” by anti-mask rhetoric, and when informed of Montana’s new emergency rule, he found it “shocking.” Murphy, the state epidemiologist who guided Montana through the first year of the pandemic, said he’s similarly “disheartened” by the action taken by his former agency on an issue that he and other experts say is scientifically settled. Public health responses to the pandemic response were politicized nationally from the start, Murphy said, and that’s “not helpful when there’s a common foe involved.” COVID-19 continues to infect hundreds of people in the state each day, and nearly 2,000 Montanans have already died.

“What are we doing in Montana that’s different to combat this uptick?” Murphy asked. “The [Gianforte] administration hasn’t offered anything different other than an emergency rule that makes it harder for these schools to comply with the national recommendation. They haven’t done anything to make vaccination easier for us, either. Yet the numbers go up. … Right now with COVID, hospitals are stressed again, and that’s probably going to get a little bit worse here over the next month.”