The agency’s director has said, repeatedly, that schools without mask mandates have triple the risk of COVID outbreaks. That claim is based on very shaky science.
The debate over child masking in schools boiled over again this fall, even above its ongoing high simmer. The approval in late October of COVID-19 vaccines for 5-to-11-year-olds was for many public-health experts an indication that mask mandates could finally be lifted. Yet with cases on the rise in much of the country, along with anxiety regarding the Omicron variant, other experts and some politicians have warned that plans to pull back on the policy should be put on hold.
Scientists generally agree that, according to the research literature, wearing masks can help protect people from the coronavirus, but the precise extent of that protection, particularly in schools, remains unknown—and it might be very small. What data do exist have been interpreted into guidance in many different ways. The World Health Organization, for example, does not recommend masks for children under age 6. The European Centre for Disease Prevention and Control recommends against the use of masks for any children in primary school.
Seen in this context, the CDC has taken an especially aggressive stance, recommending that all kids 2 and older should be masked in school. The agency has argued for this policy amid an atmosphere of persistent backlash and skepticism, but on September 26, its director, Rochelle Walensky, marched out a stunning new statistic: Speaking as a guest on CBS’s Face the Nation, she cited a study published two days earlier, which looked at data from about 1,000 public schools in Arizona. The ones that didn’t have mask mandates, she said, were 3.5 times as likely to experience COVID outbreaks as the ones that did.
This estimated effect of mask requirements—far bigger than others in the research literature—would become a crucial talking point in the weeks to come. On September 28, during a White House briefing, Walensky brought up the 3.5 multiplier again; then she tweeted it that afternoon. In mid-October, with the school year in full swing, Walensky brought up the same statistic one more time.
But the Arizona study at the center of the CDC’s back-to-school blitz turns out to have been profoundly misleading. “You can’t learn anything about the effects of school mask mandates from this study,” Jonathan Ketcham, a public-health economist at Arizona State University, told me. His view echoed the assessment of eight other experts who reviewed the research, and with whom I spoke for this article. Masks may well help prevent the spread of COVID, some of these experts told me, and there may well be contexts in which they should be required in schools. But the data being touted by the CDC—which showed a dramatic more-than-tripling of risk for unmasked students—ought to be excluded from this debate. The Arizona study’s lead authors stand by their work, and so does the CDC. But the critics were forthright in their harsh assessments. Noah Haber, an interdisciplinary scientist and a co-author of a systematic review of COVID-19 mitigation policies, called the research “so unreliable that it probably should not have been entered into the public discourse.”
