“We lack credible evidence for benefits of masking kids aged 2 to 5, despite what the American Academy of Pediatrics says,” Jeffrey Flier, former dean of Harvard Medical School, wrote recently. While there are models, and simulations on mannequins with masks, “mechanistic studies are incapable of anticipating and tallying the effects that emerge when real people are asked to do real things in the real world,” Vinay Prasad of UCSF wrote in a critique of the CDC’s child masking recommendation. “The CDC cannot ‘follow the science’ because there is no relevant science.”
This question of “relevant science” is what makes the Georgia study worth careful consideration. Over and over, studies and reports on children in schools with low transmission rates claim in their summaries that masking students helped keep transmission down. But looking at the underlying data in these studies, masks were always required or widely worn, and implemented in concert with a variety of other interventions, such as increased ventilation. Without a comparison group that didn’t require student masking, it’s difficult or impossible to isolate the effect of masks. (This is the error made by Duke University researchers who wrote a report about North Carolina schools, later summarized in a New York Times opinion piece.) I reviewed 17 different studies cited by the CDC in its K-12 guidance as evidence that masks on students are effective, and not one study looked at student mask use in isolation from other mitigation measures, or against a control. Some even demonstrated that no student masking correlated with low transmission.
Children are less likely to have severe disease from SARS-CoV-2, and when infected less likely to be symptomatic, which correlates with lower contagiousness. Those facts alone may account for part of the reason why the Georgia study found no clear benefit for a masking requirement for kids in schools. Though the CDC says that layered mitigation in schools is effective, without studying each of the layers individually, it cannot know which of those measures work, and to what degree, and which don’t. For example, several experts told me, it’s entirely possible that open windows or fresh-air ventilation accounts for nearly all the mitigation benefit in a classroom and other “layered” interventions may contribute only a marginal benefit or none at all.
While masks offer some protection for adults in many environments, as the adage in pediatrics goes, children are not little adults. Medicine is littered with examples of adult interventions that don’t translate to children.