Thread by @psychunseen

1/ Oh boy... So @MSN is legitimizing this @dcexaminer piece claiming that masks don't work to spread COVID as if it's news. It's not news!

It's an OP-ED piece written by a conservative columnist.

msn.com/en-us/health/m…

2/ The op-ed author cites a new @CochraneLibrary meta-analysis of 78 randomized controlled trials (RCTs)—describing it as a "massive mega-study"—to claim that masks don't stop the spread of COVID-19.

But the analysis only included 6 RCTs that involved COVID-19! Not massive!

3/ The analysis looked at several interventions other than masks... leaving only 12 studies that looked at surgical masks (w/ only 2/12 involving COVID) and 5 looked at N95s (none of which involved COVID)!

Now, it's true that the effect of surgical masks vs. no masks was weak...

4/ ...and that N95 masks did not improve outcomes compared to surgical masks, but there were NO studies—ZERO—that compared N95 masks to no masks.

So, there were NO RCTs that found that N95 masks do not prevent the spread of COVID!

5/ Meanwhile, since the Cochrane review only included RCTs, the many non-RCT studies that do provide evidence that masks are effective in preventing spread of COVID were NOT INCLUDED!

Like these reviewed from a @JAMA_current review:

jamanetwork.com/journals/jama/…

6/ I cited several of these in a previous tweet:

https://twitter.com/psychunseen/status/1472233774775603203?s=20&t=20vG_sE-snmRYMKjfhLDJw

7/ Including this one that concluded "that 20 days after becoming mandatory face masks have reduced the number of new infections by around 45%."

pnas.org/doi/10.1073/pn…

8/ Here's a brand new health policy study of mask mandates that found that "total infections in the US on November 15, 2020 would have been 23.7 to 30.4 percent lower if a national mask mandate had been enacted on May 15, 2020."

pubmed.ncbi.nlm.nih.gov/36495804/

9/ And here's a longer review of the many other sources of evidence that supports the use of masks to spread COVID and other infectious diseases:

kxan.com/news/coronavir…

10/ Now, to be fair, masks aren't a magic bullet and—not unlike condoms and seatbelts—are only as effective as they are worn properly.

Indeed, the @CochraneLibrary review makes clear that the evidence for masks was compromised by poor adherence.

11/ It's also probably true that the effectiveness of cloth masks is limited.

In the hospital, the standard is for healthcare workers to use N95 masks with FIT testing that helps to ensure they're worn properly.

12/ Despite treating COVID (+) patients in the hospital this past winter, I did not catch COVID thanks to an N95 mask with full PPE.

It was only after my child caught it at school, where kids have long since stopped masking, that I got COVID for the first time in 3 years.

13/ So, the bottom line is that contrary to this new headline, there is in fact plenty of evidence that masks prevent transmission of COVID despite the limited RCT data.

And aside from inconvenience, the downside is pretty minimal.

So #MaskUp #WearAMask

@CaulfieldTim @gorskon @angie_rasmussen @EricTopol @PeterHotez @SkepticsGuide

14/ P.S. Someone pointed me to the fact that one of the Cochrane review authors has strong anti-mask opinions, including denying that COVID is airborne and seemingly being more concerned about acne as a side effect than any protective effect of masking.

cbc.ca/amp/1.5994889

@threadreaderapp please unroll