Face masks effectively limit the probability of SARS-CoV-2 transmission

You rock dude ignore these haters king

"Some people with swine flu travelled on a plane from New York to China, and many fellow passengers got infected. Some researchers looked at whether passengers who wore masks throughout the flight stayed healthier. The answer was very much yes. They were able to track down 9 people who got sick on the flight and 32 who didn’t. 0% of the sick passengers wore masks, compared to 47% of the healthy passengers. Another way to look at that is that 0% of mask-wearers got sick, but 35% of non-wearers did."

https://slatestarcodex.com/2020/03/23/face-masks-much-more-t...

At the beginning of the pandemic I was skeptical about the effectiveness of masks and this article is what convinced me that there is some benefit.

> observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease

Which is also not entirely true. There are quite a lot of regions (data from worldometer, statista) that have a better control of the virus despite people not giving a crap about face masks. For instance, Florida has 1600 deaths/M vs 3000 deaths/M in New Jersey. What'd be the explanation?

> Meanwhile, they ignore the dozens of studies showing masks are ineffective, or even counterproductive

Let's try to figure out how well your summary is actually supported by your citations, especially as TFA is about medical masks and N95 masks and doesn't mention cloth masks.

TL;DR: It's not (and ignores the multiple studies showing surgical and N95 masks are effective to prevent SARS-CoV infections).

What your citations say is "cloth masks seem ineffective (but not surgical/N95), masks in general seem to protect less from influenza than coronaviruses, and wearing a mask may have some effect on exercise (although magnitude of the effect and consequences are unclear)". I wouldn't have had a problem with that statement. Whether that's the whole story or cherry-picking of studies is another question.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/

(2015) Shows that cloth masks are less effective than medical masks... and incidentally that medical masks are effective. One study in, already contradicts your statement.

https://pubmed.ncbi.nlm.nih.gov/29395560/

(2017) Not about mask efficacy in disease prevention, but effects on exercise. No difference in distance, heart rate, O2 saturation, but 20% higher shortness of breath.

https://pubmed.ncbi.nlm.nih.gov/32590322/

(2020) Not about mask efficacy in disease prevention, but effects on exercise again. Also, not an experimental study but a comment/hypothesis.

https://pubmed.ncbi.nlm.nih.gov/15340662/

(2004) Not about mask efficacy in disease prevention, again. Study on patients with end-stage renal disease.

https://pubmed.ncbi.nlm.nih.gov/26579222/

(2015) Not about mask efficacy in disease prevention, again. Study on pregnant women.

https://pubmed.ncbi.nlm.nih.gov/31159777/

(2019) First interesting one. Show that viruses may deposit on the outer surface of medical masks. May prove useful in educating people to handle with care (although it seems that contamination by touching contaminated surfaces accounts for a negligible amount).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/

(2012) Ah, better. Review of a small number of other studies, focused on influenza and close contact with an infected patient. Does not conclude masks are ineffective, but more that good data and studies are hard to come by, that the studies they reviewed were between inconclusive and positive, and they may be protective when combined with other hygiene practices. Also notes that the studies on SARS coronavirus transmission found masks protective, but the results may or may not apply for influenza. It also notes compliance and correct usage are likely factors in reduced effectiveness.

So, while this is the closest so far to your assertion, it doesn't quite support it either. Annex 5 in particular shows that the SARS coronavirus studies reviewed seem to show a protective effect.

Much larger and wider reviews, that include this one, reach different conclusions for the topic at hand. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8084286/ and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718106/

https://pubmed.ncbi.nlm.nih.gov/19216002/

(2008) Lol. Study on 32 health-care workers, and the incidence of common cold. There was 1 cold in each group. Sample way too small to reach any conclusion, as they themselves conclude.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/

Same article as the first one in the list.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2493952/pdf/ann...

(1981) Interesting, although a small trial study. But it only cares about a very specific thing: the efficiency of masks in surgery to avoid contaminating an open wound, unrelated to the airborne spread of respiratory diseases. More studies and reviews have followed, with mitigated results, see for example https://pubmed.ncbi.nlm.nih.gov/33039336/

Interesting but irrelevant for the topic at hand.

https://www.nap.edu/catalog/25776/rapid-expert-consultation-...

(2020) Expert consultation, limited to the effectiveness of homemade fabric masks. It says verbatim: "It does not apply to either N95 respirators or medical masks." (and it doesn't even conclude that homemade cloth masks are ineffective, only that more research is required).

https://www.nap.edu/read/25776/chapter/1#6

That's the same as the article just above. Could be the 2nd honest error of course, or could be a sign you've copy/pasted part or all of the list with little editing/proofreading.

https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

(2020) Review of multiple measures against influenza contamination, that seems to show no effectiveness. The authors point out themselves the limitations of the study however, small sample size and compliance issues. It's an interesting data point, but it targets influenza and I wouldn't say it disproves masks effectiveness.

When looking at the bigger picture, and more and larger review, doesn't yield the same conclusions. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718106/ that includes this study among those reviewed. Interestingly, it seems to show much more conclusive results for coronavirus infection prevention than influenza, and cautions against cloth masks.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599448/

(2019) Physical study of filtering efficiency of cloth masks vs surgical masks, especially after washing

https://www.acpjournals.org/doi/10.7326/M20-1342

(2020) One of many physical studies on patients coughing in a petri dish with various mask types. Only 4 patients, and one of the only such physical studies I've seen that didn't show a significant effect.

https://link.springer.com/article/10.1007/s00392-020-01704-y

(2020) Another one that talks about exercise and not infection.

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Looking in general at country-level data, using masks earlier seems to be significantly associated with lower mortality. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695060/ for a wide study and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7392429/ for a small comment

interesting; the same kind of erroneous supposition modeling MO is used to pretend that humans are "cooking the planet" (or is it an ice age? I guess it depends on the decade...).