Thursday, October 15, 2020

Face masks are ineffective against COVID-19

It is plausible that face masks help prevent disease, but scientific proof is lacking. The CDC and others cite a JAMA study for authority:
Americans are increasingly adopting the use of cloth face masks to slow the spread of COVID-19, and the latest science may convince even more to do so.

In an editorial published today in the Journal of the American Medical Association (JAMA), CDC reviewed the latest science and affirms that cloth face coverings are a critical tool in the fight against COVID-19 that could reduce the spread of the disease, particularly when used universally within communities.

That refers to this JAMA article:
In this issue of JAMA, Wang et al present evidence that universal masking of health care workers (HCWs) and patients can help reduce transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. ...

However, after the universal masking policy was in place, the proportion of symptomatic HCWs with positive test results steadily declined, from 14.7% to 11.5% (a mean decrease of 0.49% per day). Although not a randomized clinical trial, this study provides critically important data to emphasize that masking helps prevent transmission of SARS-CoV-2.

Got that? Positive test results only declined from 14.7% to 11.5%!

This was published in the second-most prestigious American medical journal, but it is really a crappy study. The effect was barely measurable, and there was no control group.

While one particular Massachussetts hospital did show a slight decline in positive tests, the other hospitals were showing larger declines at the same time. The declines could have been due to increased testing, less disease prevalence, or even just containment of one outbreak. I don't know.

This is a junk study, and it should not have been published without a control group. And it certainly should not have been used to set national policy.

Here is more CDC advice:

On Sept. 16, our esteemed CDC Director, Dr. Robert Redfield, told tried to sell our Senate — and the rest us — a fresh bottle of snake oil on the subject of universal masking. “Masks are the most important, powerful public health tool we have,” Redfield said, holding a surgical mask — not an N95 mask — in his hand. “And I will continue to appeal for all Americans, all individuals in our country, to embrace these face coverings.” “These actually, we have clear scientific evidence they work, and they are our best defense. I might even go so far as to say this face mask is more guaranteed to protect me against COVID than when I take a COVID vaccine.” Curiously enough, a meta-study published by the CDC in May of this year included the following conclusion about measures for containing influenza — a coronavirus — including wearing face masks: “Evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of lab-confirmed influenza.”
So the CDC contradicts itself.

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