4 ms·

Is the science flimsy? I genuinely thought that the science was very clear that good masking reduces the rate of community transmission?

miles 5y ago
The large study from Bangladesh last year[0] which was widely trumpeted with headlines like "Large Study Confirms Masks Work to Limit COVID-19 Spread"[1], averred that, "Villages where cloth masks were distributed experienced a 9 percent reduction in symptoms, while villages where surgical masks were distributed saw a reduction of 12 percent." Stanford Medicine's assessment[2] states that, "Although there were also fewer COVID-19 cases in villages with cloth masks as compared to control villages, the difference was not statistically significant." [0] https://www.poverty-action.org/study/impact-mask-distribution-and-promotion-mask-uptake-and-covid-19-bangladesh https://www.poverty-action.org/study/impact-mask-distributio... [1] https://www.webmd.com/lung/news/20210907/masks-limit-covid-spread-study https://www.webmd.com/lung/news/20210907/masks-limit-covid-s... [2] https://med.stanford.edu/news/all-news/2021/09/surgical-masks-covid-19.html https://med.stanford.edu/news/all-news/2021/09/surgical-mask...
- hedgehog 5y ago
  To put those in context, what the study did was promote masks across a bunch of villages. Some people across all arms of the study were already wearing masks of various sorts, so the data should be read as the combined effect of: the promotion changing behavior, people starting to use masks or replacing their existing ones, and then the net effect on transmission. So the % effectiveness quoted is the effectiveness of the new masks relative to whatever people were already doing watered down by how much putting up posters etc actually changes human behavior. Pretty remarkable actually.
- kyrra 5y ago
  There are some critiques of the Bangladesh study, you can read some here: https://mobile.twitter.com/Emily_Burns_V/status/1433122124768714753?s=20 https://mobile.twitter.com/Emily_Burns_V/status/143312212476... One big issue was that the mask pickup didn't equally reduce cases across ages. This leads to the training for wearing masks may have caused older groups to stop socializing, rather than the masks doing anything.
daveevad 5y ago
One of the very first studies posted to the CDC website about mask efficacy, "Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy — Springfield, Missouri, May 2020," appeared to indicate masks were overwhelmingly effective. The success of this study has not been replicated to my knowledge. https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm > Among 139 clients exposed to two symptomatic hair stylists with confirmed COVID-19 while both the stylists and the clients wore face masks, no symptomatic secondary cases were reported; among 67 clients tested for SARS-CoV-2, all test results were negative. Adherence to the community’s and company’s face-covering policy likely mitigated spread of SARS-CoV-2.

miles 5y ago

The large study from Bangladesh last year[0] which was widely trumpeted with headlines like "Large Study Confirms Masks Work to Limit COVID-19 Spread"[1], averred that, "Villages where cloth masks were distributed experienced a 9 percent reduction in symptoms, while villages where surgical masks were distributed saw a reduction of 12 percent." Stanford Medicine's assessment[2] states that, "Although there were also fewer COVID-19 cases in villages with cloth masks as compared to control villages, the difference was not statistically significant." [0] https://www.poverty-action.org/study/impact-mask-distribution-and-promotion-mask-uptake-and-covid-19-bangladesh https://www.poverty-action.org/study/impact-mask-distributio... [1] https://www.webmd.com/lung/news/20210907/masks-limit-covid-spread-study https://www.webmd.com/lung/news/20210907/masks-limit-covid-s... [2] https://med.stanford.edu/news/all-news/2021/09/surgical-masks-covid-19.html https://med.stanford.edu/news/all-news/2021/09/surgical-mask...

hedgehog 5y ago
To put those in context, what the study did was promote masks across a bunch of villages. Some people across all arms of the study were already wearing masks of various sorts, so the data should be read as the combined effect of: the promotion changing behavior, people starting to use masks or replacing their existing ones, and then the net effect on transmission. So the % effectiveness quoted is the effectiveness of the new masks relative to whatever people were already doing watered down by how much putting up posters etc actually changes human behavior. Pretty remarkable actually.
kyrra 5y ago
There are some critiques of the Bangladesh study, you can read some here: https://mobile.twitter.com/Emily_Burns_V/status/1433122124768714753?s=20 https://mobile.twitter.com/Emily_Burns_V/status/143312212476... One big issue was that the mask pickup didn't equally reduce cases across ages. This leads to the training for wearing masks may have caused older groups to stop socializing, rather than the masks doing anything.

daveevad 5y ago

One of the very first studies posted to the CDC website about mask efficacy, "Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy — Springfield, Missouri, May 2020," appeared to indicate masks were overwhelmingly effective. The success of this study has not been replicated to my knowledge. https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm > Among 139 clients exposed to two symptomatic hair stylists with confirmed COVID-19 while both the stylists and the clients wore face masks, no symptomatic secondary cases were reported; among 67 clients tested for SARS-CoV-2, all test results were negative. Adherence to the community’s and company’s face-covering policy likely mitigated spread of SARS-CoV-2.