1/ TL:DR - @who published a massive review/meta-analysis of interventions for flu epidemics in 2019, found "moderate" evidence AGAINST using masks. (They actually missed the 2015 Vietnam study, yet another brick in the wall.)

2019. So recent, yet so long ago. What's changed?

2/ Let's talk about masks, baby! Let's talk about you and me! Let's talk abouuuut masks!

Last year, @who - you may have heard of them, public health experts, friend to all nations but especially China - conducted a review of "non-pharmaceutical interventions" for flu epidemics.

3/ The review remains on the WHO Website, though it's no longer easy to find. It is, to be blunt, a long list of failure.

Handwashing? No evidence it works.
Respiratory etiquette (aka sneezing into your shirt)? No evidence.
Surface cleaning? No evidence.

https://apps.who.int/iris/bitstream/handle/10665/329438/9789241516839-eng.pdf?ua=1

4/ Despite the lack of evidence, @who goes ahead and bravely recommends all these interventions - more or less on general principles. They are "feasible," they have few "resource considerations," they are "acceptable."

In other words, why not?

5/ Now, as for masks: along with the report, @who published an even longer annex with the studies used in making the recommendations. Here’s the takeaway: 10 studies, no evidence of benefit. https://apps.who.int/iris/bitstream/handle/10665/329439/WHO-WHE-IHM-GIP-2019.1-eng.pdf?ua=1

6/ Think I’m lying? Or “misrepresenting” (my favorite word!) the @who finding? Well, here’s what THEY said in the main report:

7/ Now, despite this lack of what some nutty skeptics would call “proof” or “scientific evidence,” @who choked out a “conditional” recommendation that in “severe epidemics,” asymptomatic people might want to wear masks - “although there is no evidence that this is effective.”

8/ By the way, #SARSCoV2 doesn't even clearly meet the definition of "severe epidemic" or "pandemic" in the @who report. It falls somewhere between a typical flu season and the three big 20th century flu pandemics, mainly because it poses almost no risk to kids or healthy adults.

9/ Again, this report came out not a generation or even a decade ago but in 2019. (And let’s not even start with what it says about lockdowns.)

MASKS WERE USELESS LAST YEAR. WHAT HAS CHANGED?