One imagines that public health authorities place a very high value on maintaining their credibility. So, when they decide to gamble their credibility by publishing and enthusiastically backing a misleading and sloppy study, you have to wonder what made the health officials believe it was worth it.

Rochelle Walensky, who is President Joe Biden’s director of the Centers for Disease Control and Prevention, has spent months touting a study that purports to show a massive benefit from forcing little children to wear masks all day at school. That study shows nothing of the sort.

Walensky first touted the mask study on Face The Nation in September. The CDC, she said, “published a study out of Arizona that demonstrated that places that had no masks in place were three and a half times more likely to have outbreaks than places that did have masks in place.”

Atlantic writer David Zweig spoke to eight experts who showed him just how flawed this study was. In short, the study didn’t count how many children got infected, but rather how many “outbreaks” occurred, with an outbreak defined as two epidemiologically linked cases. So, if two children got sick at a weekend party, that was an outbreak. If 12 children got each other sick on the school bus, that’s a single outbreak. This is hardly a finely tuned study.

What’s more, the unmasked students were in school slightly more than the masked students, which at least partly explains the greater number of outbreaks among the unmasked.

Most damning to these findings: Masked students were, due to their masking, not counted as close contacts, thus they were probably not tested as much as close contacts. If you test the unmasked schools more than you test the masked schools, are you surprised that you find more cases at the unmasked schools? The CDC study, of course, had no data on severe cases in these Arizona schools.

The CDC study didn’t control for other factors such as ventilation, vaccination, or other mitigation efforts. In my experience, the most masked places are the most vaxxed places and the most distanced places.

Zweig digs up more problems, including the study counting institutions from the wrong county or counting vocational schools. Nevertheless, Walensky has been relentless in promoting this study on Twitter and TV.

This is the sort of thing that will drive more and more people to assume the CDC, the FDA, or other health authorities are either clueless or dishonest. So, why does school masking matter so much to Walensky and presumably Biden that they are willing to torch their credibility?

The biggest hint we have is the CDC's deference to teachers unions on the question of reopening schools. The best guess on masks is that teachers unions wanted cover for forcing children into masks, and Walensky provided it. That's good governance. Or not.