Margery Smelkinson is an infectious-disease scientist whose research has focused on influenza and SARS-CoV-2. Leslie Bienen is a veterinarian and faculty member at the OHSU-Portland State University School of Public Health. Jeanne Noble is an emergency medicine doctor at UCSF.
In the panicked spring of 2020, as health officials scrambled to keep communities safe, they recommended various restrictions and interventions, sometimes in the absence of rigorous science supporting them. That was understandable at the time. Now, however, two years into this pandemic, keeping unproven measures in place is no longer justifiable. Although no district is likely to roll back COVID policies in the middle of the Omicron surge, at the top of the list of policies we should rethink once the wave recedes is mandatory masks for kids at school.
The CDC guidance on school masking is far-reaching, recommending “universal indoor masking by all students (age 2 and older), staff, teachers, and visitors to K–12 schools, regardless of vaccination status.” In contrast, many countries—the U.K., Sweden, Norway, Denmark, and others—have not taken the U.S.’s approach, and instead follow World Health Organization guidelines, which recommend against masking children ages 5 and younger, because this age group is at low risk of illness, because masks are not “in the overall interest of the child,” and because many children are unable to wear masks properly. Even for children ages 6 to 11, the WHO does not routinely recommend masks, because of the “potential impact of wearing a mask on learning and psychosocial development.” The WHO also explicitly counsels against masking children during physical activities, including running and jumping at the playground, so as not to compromise breathing.
But in America about half of the country’s 53 million children remain compulsorily masked in school for the indefinite future. Sixteen U.S. states and the District of Columbia follow the CDC guidance closely and require masks for students of all ages, regardless of vaccination status; other states rely on a patchwork of policies, usually leaving decisions up to local school districts. (Nine states have banned school mask mandates, though in five of them, lawsuits have delayed implementation of the ban.) Many deep-blue areas such as Portland, Oregon; Los Angeles; and New York City have gone beyond CDC guidance and are masking students outdoors at recess, in part because of byzantine rules that require an unmasked “exposed” student to miss multiple days of school, even if the putative exposure is outside.
Read: The CDC’s flawed case for wearing masks in school
Many public-health experts maintain that masks worn correctly are essential to reducing the spread of COVID-19. However, there’s reason to doubt that kids can pull off mask-wearing “correctly.” We reviewed a variety of studies—some conducted by the CDC itself, some cited by the CDC as evidence of masking effectiveness in a school setting, and others touted by media to the same end—to try to find evidence that would justify the CDC’s no-end-in-sight mask guidance for the very-low-risk pediatric population, particularly post-vaccination. We came up empty-handed.
To our knowledge, the CDC has performed three studies to determine whether masking children in school reduces COVID-19 transmission. The first is a study of elementary schools in Georgia, conducted before vaccines became available, which found that masking teachers was associated with a statistically significant decrease in COVID-19 transmission, but masking students was not—a finding that the CDC’s masking guidelines do not account for.
A second and more recent study of Arizona schools in Maricopa and Pima Counties concluded that schools without mask mandates were more likely to have COVID-19 outbreaks than schools with mask mandates. Yet more than 90 percent of schools in the “no mask mandate” group were in Maricopa County, an area that has significantly lower vaccination rates than Pima County. This study had other serious shortcomings, including failure to quantify the size of outbreaks and failure to report testing protocols for the students.
The third CDC study found that U.S. counties without mask mandates saw larger increases in pediatric COVID-19 cases after schools opened, but again did not control for important differences in vaccination rates. The CDC has cited several other studies conducted in the previous school year to support its claim that masks are a key school-safety measure. However, none of these studies, including ones conducted in North Carolina, Utah, Wisconsin, and Missouri, isolated the impact of masks specifically, because all students were required to mask and no comparisons were made with schools that did not require masks.
Therefore, the overall takeaway from these studies—that schools with mask mandates have lower COVID-19 transmission rates than schools without mask mandates—is not justified by the data that have been gathered. In two of these studies, this conclusion is undercut by the fact that background vaccination rates, both of staff and of the surrounding community, were not controlled for or taken into consideration. At the time these studies were conducted, when breakthrough infections were much less common, this was a hugely important confounding variable undermining the CDC’s conclusions that masks in schools provide a concrete benefit in controlling COVID-19 spread: Communities with higher vaccination rates had less COVID-19 transmission everywhere, including in schools, and those same communities were more likely to have mask mandates.
This isn’t to say that these studies conclusively demonstrate that masks have no benefit in schools, but that any effect they have, if they have one, is tangled up in these other variables. To demonstrate any independent effect of masks on COVID-19 transmission would have required comparing communities with similar vaccination rates or statistically controlling for differences in vaccination rates, including by specific groups such as teachers and students. Without making these adjustments, it is impossible to attribute differences in case rates, let alone differences in in-school transmission, to mask wearing in school.
At least pre-Omicron, adjusting for vaccination rates in the surrounding community was vitally important when looking at case rates. Comparisons of counties in California that did and did not have mask mandates showed that vaccination rates were highly predictive of hospitalization rates, but mask mandates were not. Neighboring Los Angeles and Orange Counties, which had similar vaccination rates but differing masking requirements, had similar case and hospitalization rates. Likewise, our analyses of data from Maryland show a tight correlation between hospitalizations and immunity rates by county, despite some counties requiring masks in all indoor facilities, some requiring masks only in county buildings, and some not requiring masks at all.
Vinay Prasad: The downsides of masking young students are real
To justify mask requirements in school at this point, health officials should be able to muster solid evidence from randomized trials of masking in children. To date, however, only two randomized trials have measured the impact of masks on COVID transmission. The first was conducted in Denmark in the spring of 2020 and found no significant effect of masks on reducing COVID-19 transmission. The second is a much-covered study conducted in Bangladesh that reported that surgical masks (but not cloth) were modestly effective at reducing rates of symptomatic infection. However, neither of these studies included children, let alone vaccinated children.
Other studies—not randomized trials—have looked at the effects of masks in schools, and their results do not support pervasive, endless masking at school. A study from Brown University, analyzing 2020–21 data from schools in New York, Massachusetts, and Florida, found no correlation between student cases and mask mandates, but did see decreased cases associated with teacher vaccination. A study published in Science looking at individual mitigation measures in schools last winter found that, although teacher masking reduced COVID-19 positivity, student masking did not have a significant effect.
Even though the first half of this school year was dominated by the highly transmissible Delta variant, the picture in more recent studies looks similar. In Tennessee, two neighboring counties with similar vaccination rates, Davidson and Williamson, have virtually overlapping case-rate trends in their school-age populations, despite one having a mask mandate and one having a mask opt-out rate of about 23 percent. One would expect a quarter of the students opting out of masking to affect transmission rates if masks played any significant role in controlling COVID-19 spread, but that was not the case. Another recent analysis of data from Cass County, North Dakota, comparing school districts with and without mask mandates, concluded that mask-optional districts had lower prevalence of COVID-19 cases among students this fall. Analyses of COVID-19 cases in Alachua County, Florida, also suggest no differences in mask-required versus mask-optional schools. Similarly, the U.K. recently reported finding no statistically significant difference in absences traced to COVID-19 between secondary schools with mask mandates and those without mandates.
Despite how widespread all-day masking of children in school is, the short-term and long-term consequences of this practice are not well understood, in part because no one has successfully collected large-scale systematic data and few researchers have tried. Mental and social-emotional outcomes are hard to observe and measure, and can take years to manifest. Initial data, however, are not reassuring. Recent prospective studies from Greece and Italy found evidence that masking is a barrier to speech recognition, hearing, and communication, and that masks impede children’s ability to decode facial expressions, dampening children’s perceived trustworthiness of faces. Research has also suggested that hearing-impaired children have difficulty discerning individual sounds; opaque masks, of course, prevent lip-reading. Some teachers, parents, and speech pathologists have reported that masks can make learning difficult for some of America’s most vulnerable children, including those with cognitive delays, speech and hearing issues, and autism. Masks may also hinder language and speech development—especially important for students who do not speak English at home. Masks may impede emotion recognition, even in adults, but particularly in children. This fall, when children were asked, many said that prolonged mask wearing is uncomfortable and that they dislike it.
This last reason is important in considering a pivot to requiring children to wear N95 or KN95 masks, which are thought to be more effective at preventing the spread of Omicron. A few school districts, in response to the growing awareness of the ineffectiveness of cloth and surgical masks, have decided to escalate rather than scale back masking by requiring these types of medical-grade masks, which are significantly less comfortable to wear and can hinder communication more than other types of masks.
Read: Why are Americans still—still!—wearing cloth masks?
As with our existing school-mask policies, no real-world data indicate that these masks decrease transmission in school settings—data that matter greatly, as these masks require a very tight fit to function effectively, and that may not be possible for many kids. N95s are not approved or sized for children, proper fit is hard to achieve even with adults, and a June 2020 study shows they have very high failure rates when taken on and off or worn for multiple hours. Though KN95s, the manufactured-in-China equivalent, are available in kids’ sizes, they also require a very tight seal to function properly, which is unrealistic for schoolchildren to maintain for multiple hours a day. Early-pandemic recommendations to mask at school, soon followed by mandates, were laid down in the absence of data. We should not repeat this mistake with a new generation of masks.
Over the past 21 months, slowly and with much resistance, the layers of mythology around COVID-19 mitigation in schools have been peeled away, each time without producing the much-ballyhooed increases in COVID-19. Schools did not become hot spots when they reopened, nor when they reduced physical distancing, nor when they eliminated deep-cleaning protocols. These layers were peeled away because the evidence supporting them was weak, and they all had substantial downsides for children’s education and health.
Masking is the last and most stubborn layer, possibly because its drawbacks are more subtle and not yet well documented. We understand that many public-health professionals and parents may want to keep that layer in place, perhaps because they think the possible drawbacks to masking are even less well quantified than the possible benefits. They may point to the low vaccination rate among children to argue against any loosening of mitigation measures, even if they cannot directly connect those measures to reduced transmission. They may also point to the Omicron surge increasing children’s hospitalizations. But hospitalizations have risen among all age groups, and, even at the country’s peak, remained extremely low among children, on par with pediatric flu hospitalizations during a typical season.
Imposing on millions of children an intervention that provides little discernible benefit, on the grounds that we have not yet gathered solid evidence of its negative effects, violates the most basic tenet of medicine: First, do no harm. The foundation of medical and public-health interventions should be that they work, not that we have insufficient evidence to say whether they are harmful. Continued mandatory masking of children in schools, especially now that most schoolchildren are eligible for vaccination, fails this test.