NYC Health Department now recommends double masking to fight COVID-19

Double masking is guaranteed by the NYC, NY, and Pa health departments to protect you against viruses larger than pea gravel or double your life back.

Im for wearing plastic bags over their heads with zip tyes

Is there any evidence that one or more masks reduce transmission? Any studies?

Until Wuflu hit, years of research studies concluded face masks were ineffective for respiratory viruses. TPTB wanted faces masks, so researchers cranked out some studies saying masks work. The CDC recently released a study saying masks work. The data analysis only ran until October, well before the fall surge in cases got underway.

Thx, will check when I’m home.

CDC links to studies 1-27 generally talk about how masks stopped particles, but have nothing on how much transmission was reduced.

Study 28 did a systematic review and meta-analysis to investigate the optimum distance and the use of masks and eye protection. Transmission of virus was lower with distance - moderate certainty. It continues ... “Face mask use could result in a large reduction in risk of infection ... low certainty ... with stronger associations with N95 ... compared with disposable ... low certainty”

Their search did not identify any randomised trials. IIRC, aren’t randomised trials the gold standard?

Figure 4 has apparently compelling stats showing events/face mask = 163/3,686 = 4.4% and events/no face mask = 546/6,484 = 8.4% - almost twice as high. There’s one suspicious setting for China/Covid with 1/1,286 for mask and 119/4,036, but there’s still a big disparity without this setting.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext

Study 32 discusses two hair stylists with positive test results worked on 139 clients with everyone wearing masks. None of the clients had positive test results. I wondered whether the hair stylists might have had false positives. Stylist A had 4 close contacts who tested positive; Stylist B had 2 who did not. Interesting result, not sure I want to put too much weight on what might have been one individual who didn’t transmit during relatively short interactions (mean 19.5 minutes).
https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm?s_cid=mm6928e2_w

Study 33 indicated that mask use was 79% effective before symptom onset, but not after. Close frequent contact and diarrhea were particularly dangerous.
https://gh.bmj.com/content/5/5/e002794

I did not look at the last 12 studies, as I am out of time.

I checked the CDC website in September and December for studies that had results on mask effects on virus transmission. They didn’t have anything then. It looks like there is some evidence that masks are helpful. Whether they are worth the negative effects of masks is a different question.

Background info for anyone still reading:

CDC has a Guide to Masks page: https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/about-face-coverings.html

This page has links for Masks and Recent Studies:
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/diy-cloth-face-coverings.html
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover-guidance.html#recent-studies

The Masks page has no obvious links to recent studies. There is a link to a video of CDC employees saying I wear a mask because ... Not one of them talks about reduced transmission or any evidence thereof. The fact that the people who would know about the evidence don’t mention it makes me wonder if there is any such evidence.

The Recent Studies link goes to a page called Guidance for Wearing Masks - misleading. There are 45 studies listed, most with links. There are also two slide shows - the short one has some stats on the effectiveness on masking.

The NYC health department should double their Depends.

5.56mm

Here is the report I mentioned. I had to go digging for it. It was released on 5 Feb and only covers March-October of last year.

https://www.cdc.gov/mmwr/volumes/70/wr/mm7006e2.htm?s_cid=mm7006e2_w