99% invisible recently released a good documentary about the CDC.
It shows the CDC to be (at least in some parts of its remit) incompetent. It's about the data-collection work the CDC was doing (or not doing) in 2020.
It reminds me of an article the CDC wrote in 2020, and my criticism of it at the time, for a different aspect of its work. So I post all three here together.
https://99percentinvisible.org/episode/pandemic-tracking-and-the-future-of-data/
https://www.cdc.gov/media/releases/2020/p0714-americans-to-wear-masks.html
The hairdressers anecdote. This is a dangerous study. There is no control group, so the results are 100% meaningless. That the CDC is taking this kind of story as evidence is damaging for its credibility.
That said, there is evidence that hairdressers should wear masks. It comes from the Wells curve and all the follow up research over many decades. If you are standing over someone, within 50cm-ish, then masks are an appropriate barrier measure.
That's the thing. People like CDC experts want to believe that the world is simple - mask usage is either good or bad. But the world is full of complexity, different types of situation where different behaviours are appropriate. They reject a complicated truth over a simple fiction.
(TBH even if there was a control group, you might need more info before you consider using that anecdote as evidence for anything - for example cloth face coverings and surgical masks are not the same thing! you'd need to categorise by how much time they are wearing each one, and other factors, then do some statistics ... then you know if the result is meaningful)
It's knowing the difference between a study and an anecdote/case-study.
I try not to be too dismissive. But in this case ... this is really disappointing. The CDC should do better than this, given its importance in global policy making. I, a total layman, can instantly find serious mistakes.
...and it's not just a mistake. it's a lack of curiosity. it's not being interested in what is true or false, as long as it supports your preconception. it's not being analytical at all, just following a dogma.
The CDC is revealing itself to be grossly incompetent in its role.
...even though its point about mask-wearing hairdressers is actually correct!