Found an interesting study of the efficacy of masks. Apparently, one German city required them before it’s neighbors, and when compared to people in nearby areas who had previously looked very much like this city, new covid cases dropped dramatically after the mask mandate in the masked city, and not in previously-similar cities.
Sounds like the Kansas county level study from last year.
ETA, yanketripper ninja’d me here: Opening schools increase the spread of COVID-19 ~24% - #481 by YankeeTripper
Posting this preliminarily as I’ve skimmed parts of this but haven’t read it all. A coworker posted this, and I generally trust his recommendations.
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Thanks Mathman, didn’t realize there was a MASKS thread, probably should have used search.
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An oldie but a goodie:
A pre-covid study that found disposable medical masks work better at reducing respiratory bugs among healthcare workers than cloth masks. The “control” group had results in-between, but this is almost forced as the “control” group mostly wore masks, and wore a mix of cloth and medical masks.
But cloth masks are still a whole lot better than nothing? I’d assume? the study doesn’t discuss that.
I wear a cloth mask because I prefer it over those disposable n95 but maybe I should switch up.
This is the recent Bangladeshi study.
There were 178,288 individuals in the intervention group and 163,838 individuals
in the control group. The intervention increased proper mask-wearing from 13.3% in control
villages (N=806,547 observations) to 42.3% in treatment villages (N=797,715 observations)
(adjusted percentage point difference = 0.29 [0.27, 0.31]). This tripling of mask usage was sustained during the intervention period and two weeks after. Physical distancing increased from
24.1% in control villages to 29.2% in treatment villages (adjusted percentage point difference
= 0.05 [0.04, 0.06]). After 5 months, the impact of the intervention faded, but mask-wearing
remained 10 percentage points higher in the intervention group.
The proportion of individuals with COVID-like symptoms was 7.62% (N=113,273) in the
intervention arm and 8.62% (N=13,893) in the control arm. Blood samples were collected
from N=10,952 consenting, symptomatic individuals. Adjusting for baseline covariates, the
2
intervention reduced symptomatic seroprevalence by 9.3% (adjusted prevalence ratio (aPR) =
0.91 [0.82, 1.00]; control prevalence 0.76%; treatment prevalence 0.68%). In villages randomized to surgical masks (n = 200), the relative reduction was 11.2% overall (aPR = 0.89 [0.78,
1.00]) and 34.7% among individuals 60+ (aPR = 0.65 [0.46, 0.85]). No adverse events were
reported.
They found that giving away masks and regularly encouraging people to wear them properly increased proper use from 13.3% to 42.3%, and they observed a drop of 11% in symptomatic covid overall with surgical masks (despite only 42% wearing them), and that this drop was statistically significantly less than 0, and non-significant drop in symptomatic cases in villages with cloth masks.
Looking only at those people who consented to give blood, the drops in covid rates were slightly greater, but the drop for cloth masks was still not statistically significant.
The impact was surprisingly different by age:
Figure 3: Effect on Symptomatic Seroprevalence by Age Groups, Surgical Masks Only
(a) Above 60 Years Old: down 34.7%
(b) 50-60 Years Old: down 23.0%
(c) 40-50 Years Old: no statistically significant decrease
(d) Younger than 40 Years Old: no statistically significant decrease
The Economist thinks it’s because younger people were less likely to have symptoms, and they only tested people with symptoms. I suspect it’s because older people were more likely to be in among the mask-wearers, just like they are more likely to get vaccinated, stay home, and otherwise take precautions. (But I haven’t read the whole 90 pages)
And hey, they directly answer Marcie:
Our results should not be taken to imply that masks can prevent only 10% of COVID-19 cases,
let alone 10% of COVID-19 mortality. Our intervention induced 29 more people out of every
100 to wear masks, with 42% of people wearing masks in total. The total impact with near-universal masking–perhaps achievable with alternative strategies or stricter enforcement–may be
several times larger than our 10% estimate. Additionally, the intervention reduced symptomatic
seroprevalence more when surgical masks were used, and even more for the highest-risk individuals in our sample (23% for ages 50-60 and 35% for ages 60+). These numbers likely give a better
sense of the impact of our intervention on severe morbidity and mortality, since most of the disease
burden is borne by the elderly. Where achievable, universal mask adoption is likely to have still
larger impacts.
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One interesting point in the Bangledeshi study is that they explicitly told participants that they can wash and re-use the “disposable” masks, and they found that after a number of washings, they still filtered pretty well.
The cloth masks had three layers, but didn’t include an actual “filter” layer, as best as I can tell. So I’d say they were medium-quality as cloth masks go. Their point estimate for the impact of cloth masks was a decrease in cases, but it wasn’t statistically significant. I think the reduction in symptoms WAS statistically significant. Only about 40% of participants let them draw blood, so there’s a ton of noise in the data.
Full disclosure, I’ve only skimmed through this and haven’t gone to any of the links to the underlying studies that are in the article but here are a number of studies, many peer reviewed that do indicate that masks are effective but not perfect.
If anyone wants to go on a deep dive into some of the links, have at it.
By the way, as I mentioned in the other thread, my recent discovery is the 3-fold, box-fitting style KF94 mask. They don’t seal as well as well-fitted N95 masks with straps behind the head. But they are a lot easier to fit moderately well, and I find they very comfortable. (Unlike the n95s, which I find uncomfortable.) They are also light and easy to breath through – nearly as light and easy to wear as surgical masks, with the bonus that they don’t touch the tip of my nose or my lips, and they sit low enough to stay completely out of the way of my glasses. The “don’t touch the lips” also means it’s easy to talk while wearing them.
I just bought a bunch, and I expect them to be my go-to masks for a while.
I got them from this source:
Special Blue KF94 3D Mask (Large Black - Adult Size) - 100pcs Special – Be Healthy (behealthyusa.net)
I also bought a couple of VOG masks.
Vogmask - Filtering Face Mask Industry Leader - High Efficiency Particulate Filter - Stylish Face Mask
They have a high-quality, tested filter, and they come in a lot of attractive options. That’s what I wear when I visit my mom. They are a little harder to breath through than the KF94 masks, but will probably be nice in the winter. 
Here are the last two paragraphs:
Thanks Lucy. I ordered some of the KN94 masks, they are really nice and comfortable. I was running low on surgical masks.
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snips from article
MIAMI — Florida’s top health official was asked to leave a meeting after refusing to wear a mask at the office of a state senator who told him she had a serious medical condition, officials have confirmed.
…
Polsky told The Associated Press about the tense exchange with state Surgeon General Joseph Ladapo that was first reported by the news site Florida Politics. She said Ladapo and two aides were offered masks and asked to wear them when they arrived for the Wednesday meeting. She did not tell him she had breast cancer, but said she had a serious condition.
The U.S. Centers for Disease Control and Prevention says cancer patients are at a higher risk to get severely ill from COVID-19 and may not build the same immunity to vaccines.
Ladapo had asked to meet her in Tallahassee as he seeks confirmation in the Senate after being named to the post by Gov. Ron DeSantis last month.
…
Democrats have opposed the appointment of Ladapo, criticizing him for comments and actions related to the pandemic.
A day into his job, Ladapo signed new rules allowing parents to decide whether their children should quarantine or stay in school after being exposed to people who tested positive for COVID-19.
On Thursday at a press conference with DeSantis to oppose vaccine mandates, Ladapo said people were not comfortable with the vaccines because the federal government has not been open about the effectiveness and safety of the vaccines, saying there was a “concerted effort” to hide stories of people with adverse reactions.
…
Ladapo also wrote an opinion column in the Wall Street Journal saying masks have “little or no effect on respiratory virus transmission.”
…
“It shouldn’t take a cancer diagnosis for people to respect each other’s level of comfort with social interactions during a pandemic,” he said. “What occurred in Senator Polsky’s office was unprofessional and will not be tolerated in the Senate.”
Does he understand the magic of the internet? It’s never been this easy to check the data.
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which suggest that particles much larger than the 5-μm boundary (a number that is sometimes cited by public health authorities as a droplet/aerosol cutoff) can remain suspended in air for many minutes or more, can waft around, and, of significant consequence for public health implications for this pandemic, accumulate depending on currents of air and ventilation status of the environment
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The important part:
The available evidence suggests that near-universal adoption of nonmedical masks when out in public, in combination with complementary public health measures, could successfully reduce ReRe to below 1, thereby reducing community spread if such measures are sustained. Economic analysis suggests that mask wearing mandates could add 1 trillion dollars to the US GDP
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Is the trillion from manufacturing and sales of masks?
mask mandate re-instituted in new york. 
I HATE MASKS!
What? NYC didn’t have a mask mandate? Our mask mandate was lifted for about a month back in the summer, but promptly reimplemented.
I hate them too but I think it’s for the greater good so I wear them even though they aren’t mandated here.
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