CDC director’s slippery response to criticism of school mask mandates further undermines his agency’s credibility

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Americans should be able to count on the Centers for Disease Control and Prevention (CDC) for honest and accurate information about communicable diseases and strategies to deal with them. But time and again during the COVID-19 pandemic, CDC director Rochelle Walensky has proven untrustworthy. The latest example is Walensky’s slippery response to critics of a study she repeatedly cited to justify the CDC’s controversial recommendation that K-12 schools require students to wear face masks as protection against COVID- 19.

This study, which the CDC released on September 24, looked at “school-associated COVID-19 outbreaks” – defined as two or more confirmed cases among students or staff over a 14-day period – in two counties in Arizona from July 15 to August 31. “After adjusting for the described potential confounders,” the researchers reported, “the odds of a school-associated COVID-19 outbreak in schools without a mask requirement were 3.5 times higher than those in schools with an early mask requirement. “

As I noted at the time, the study did not take into account local vaccination rates or the COVID-19 guarantees that schools adopted in addition to mask mandates. Ignoring these variables per se makes it impossible to draw firm conclusions about the explanation for the difference described by the researchers.

It is plausible that schools with “early mask requirements” tend to be located in neighborhoods with relatively high vaccination rates. It’s also plausible that they were particularly likely to take other precautions, such as better ventilation and physical distancing. These factors might help explain why schools with mask warrants were less likely to report outbreaks. Since the researchers did not control for these variables, their study cannot tell us what role the mask requirements played.

In a Dec. 16 article published by The Atlantic, David Zweig noted these and several other potential issues with the study, including the choice of outbreaks over infection rates as an outcome variable, a bias in the test. “close contact” and the fact that some schools were open twice as long as others during the study period. More generally, scientists interviewed by Zweig said the magnitude of the alleged effect was highly implausible and inconsistent with other research on the benefits of masking. Noah Haber, postdoctoral researcher at the Meta-Research Innovation Center at Stanford University and co-author of a recent systematic review of research on COVID-19 mitigation measures, described the study in Arizona as ” so unreliable that it probably shouldn’t have been made public. speech.”

Walensky nonetheless clung to the study as validation of the CDC’s support for “universal masking” in K-12 schools. In an interview with Face the Nation two days after the study’s publication, she said that she “demonstrated that places that did not have [mask mandates] in place were three and a half times more likely to have outbreaks than places that had [mask mandates] in place. “At a White House briefing two days later, she said that” the jurisdictions which have masked [requirements] at the start of their school year… were three and a half times less likely to have outbreaks. In a tweet this afternoon, she said data from Arizona “bolsters the benefits of masks” to “prevent outbreaks of # COVID19 in schools.” During a home briefing on October 13, she reiterated that “Schools without a mask requirement were three and a half times more likely to have an outbreak of COVID-19 than schools that need one.”[d] masks. “

Last week, Walensky answered viewers’ questions during a Fox News segment. “You consistently cited a study in Arizona as the rationale for school mask mandates,” noted viewer Dave Joyce. “Yet there are reports in The Atlantic that show the study to be deeply flawed. Will you follow the science and stop relying on flawed studies and end-mask warrants for children in the schools? “

Despite his great confidence in the Arizona study, Walensky failed to acknowledge, let alone refute, any of the points made by Zweig or the experts he cited. Instead, she said this:

There has been study after study, not only in this country but in other countries, that has shown that our diaper prevention strategies, including masks in schools, are able to keep our schools safe and open. What I would say now is that we have the capacity with the vaccines available now for children over 5 that we would encourage parents to get their children vaccinated. Most of all, we want to be able to keep our schools open, and the best way to do that is to use these multi-level prevention strategies, and that includes not only vaccinating our children and adults, but also continuing to mask, certainly. in the context of this highly transmissible omicron variant.

Note that Walensky is referring to “layered prevention strategies” rather than specific mask mandates. That’s because the research she alludes to has generally not attempted to isolate the impact of mask requirements. Overall, the studies haven’t even compared schools with mask mandates to schools without them. They showed that schools with “layered prevention strategies” could reopen “safely” in the sense that infection rates were generally low. They did not show, and by their design could not show, that masking or any other specific guarantee was necessary for schools to reopen “safely”.

When it first released its guidelines for schools, the CDC’s best attempt at more rigorous analysis was a large study of Georgia schools released in May, which found no statistically significant evidence that does. Forcing students to wear masks reduced infection rates, even before vaccines became widely available. In a preprint study published the same month, Brown University economist Emily Oster and four other researchers analyzed COVID-19 data from Florida, New York and Massachusetts for the 2020-2021 school year. “We find no correlation with mask warrants,” they reported. But they noted that “all rates [were] lower in the spring, after the teachers’ vaccination [was] In progress.”

In short, the CDC has decided to recommend “universal masking” of K-12 students without any solid evidence that the policy has a significant impact on the transmission of COVID-19, let alone the fact that its benefits l outweighed the substantial burdens it imposes. The CDC is now trying to retroactively validate its decision, citing subsequent research that remains far from conclusive.

School districts that still require masking are relying on the CDC’s judgment. The same goes for the Biden administration when it maintains that deviating from the agency’s advice is not only reckless but illegal. Both assume that we can count on the CDC to fairly assess the scientific evidence. The agency’s handling of this problem, along with its many other missteps, misstatements and weakly justified reversals, shows that we cannot.

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