Danish study finds face masks provide limited protection to wearer

BTW, I find cloth masks not so comfortable, but the plastic face shield is no real additional discomfort at all.

>After one month, 1.8% of the people wearing masks had been infected, while 2.1% of the people in the control group had tested positive, Copenhagen University Hospital said in a press release.

>The study does not confirm the expected halving of the risk of infection for people wearing face masks

>Participants reported their own test results; mask use was not independently verified, and users may not have worn them correctly.

So the control group had no masks, and the mask group were only told to wear a mask, and we have no data for how often they wore it. If their behavior is anything like what I'm seeing in the U.S., they're wearing it into the grocery store and going and seeing friends normally without a mask. The fact the study still produced a (likely statistically insignificant) 15% reduction in risk (1.8/2.1) is surprising under these circumstances.

it's defense in depth, and if masks, which are literally dirt cheap and only a minor inconvenience are even somewhat effective, that adds to the overall mitigation efforts and should be mandated.

It's not hard folks.

"Turning off SMTP relay only prevents other people from getting spam. I'm not going to do that, even though it's a one line configuration change and doesn't really impact my use case. Moreover, the default should be open SMTP relay"

I wear a mask every time I go to the shops. I've never been given an official briefing on how to do it. There have been about 1,300,000 coronavirus deaths worldwide.

- The point of wearing a mask is primarily to protect others, not yourself. Since we know covid has high asymptomatic infection rates, it helps control the spread of the disease for everyone to wear a mask even if they think they have no reason to stay home.

- There was no recommendation for the control group not to wear a mask.

- Very few people, percentage-wise, get covid at all, and many people are staying home, avoiding crowded events, etc. anyway. You could run a similar study demonstrating that over a month or so, a group told to wear seat belts did not get injured or die in car crashes at a higher rate than the control group, just because so few of them got in crashes at all. It would mean nothing for whether seat belts are worthwhile.

People are going to die as a result of the propaganda citing this study. I wonder if the scientists are okay with that.

There may also be an argument that it was immoral to use research money to conduct this flawed of a study in the first place.

I wish the conversation would move on from "do masks work?" to "do they work well enough to be worth the cost?"

Because I think the costs are being significantly underestimated. We are social creatures. All of the joy has been taken out of routine daily activities. Putting on a mask at the supermarket entrance as if you're about to enter some contaminated danger zone. Being unable to give a friendly smile to people as you pass them. I am 100% sure it's affecting my mental health, and I can't be the only one. In online discussion, these concerns get brushed aside as if they are the complaints of a spoiled child: "stop being a Karen and put a damn mask on..."

I'm not some science denier. It seems logical that a barrier over the mouth and nose must limit how far droplets can travel. As I understand it, empirical evidence also supports this (when the mask is worn by an infected person). There may be some (weak) evidence that masks also protect a non-infected wearer, despite this study.

But the size of the effect can't be that big. Here in the UK mask compliance is high, yet we're well into our second wave. So in the real world, masks can't be doing all that much. (Or, most of the infections are happening in mask-free places such as between family members in the home).

So maybe I'm just another "Karen", but I want more evidence that I'm enduring the costs of mask-wearing for a good reason.

In the meantime, I'll keep wearing my mask because it seems to keep everyone else happy, but I'm continually disappointed by the lack of nuanced discussion about this.

(1) It only takes one non-masked, close-contact exposure to coronavirus to become infected... that it, mostly. how it is spreading. The study does not control for the exposure risk profile of the sample populations so... there you go. This study is next to worthless...

(2) There have already been numerous studies, recently, that cloth masks are effective at filtering out particles, even down to 1-5 microns in some cases. Most cloth face masks are very effective and filtering larger particles (50-250 microns). Particle mass/volume scale with the particle diameter to the third power (i.e. V=1.33PIR^3 or 0.166PID^3). So a 100 micron particle contains 1000 times more mass/volume or viral load than an 10 micron particle and a million times more than a 1 micron particle. Thus is most important to filter the big particles in reducing viral load expelled by infected individual and breathed in by others. Cloth face masks, and surgical masks are pretty good at doing this. N95 and KN95 are already well tested in this area. So while masks can't filter out all virus... they are pretty good a significantly reducing the viral load which is important.

(3) I know people at work who became infected at a party and came to work for days while they were unknowingly infected. But thus far, there have been no "at work" coronavirus transmission cases because we wear good masks. Thus far this is true at our other sites as well. I know a local state epidemiologist who remarked to me that the overall rate of transmission in the workplace, for places with good mask protocols, is remarkably low.

https://www.acpjournals.org/doi/10.7326/M20-6817

The intervention being tested was merely how a RECOMMENDATION to wear a mask (and other advice and a pack of 50 surgical masks) may affect infection rates.

Of the mask wearers, and based on asking them and accepting their answers as truthful, 46% wore the mask as recommended, 47% "predominantly" as recommended, 7% not as recommended. The 7% were excluded from the results.

The infection in the area at the time was 2%. This gives relatively fewer chances for the efficacy of masks to be tested and so it is not surprising that the results are inconclusive. The benefit masks bring in this case is keeping the infection rate low and only actively do their job during the relatively rare times when an infected individual is near a healthy one.

The low infection rate also leads to an inflation of any systematic differences between the two samples. A very small difference applied to the expected 98% healthy subsample can lead to a strong contribution to the the 2% infected subsample. For example, mask wearing at the home was not covered and a few reported covid infections at the home.

Testing in places where infection rates are higher would have a better chance to show an effect. Of course that would be stymied by sample bias (if "random" self-selection of mask-wearers and anti-mask idiots were allowed in the procedures) or it would be faced with unethical practice of forcibly withholding masks from individuals in a non-mask sample.

My personal conclusion is that these results are not conclusive but will be hugely appropriated for whatever sick fantasy the outgoing US administration is orchestrating.

The masks most people are wearing are 'surgical masks' but those still tend to be in the 75% range. Which if both sides are wearing 75% masks, then the effectiveness is still relatively high. An effectiveness above 90%.

The article says:

“The results could indicate a more moderate degree of protection of 15-20%, however, the study could not rule out that face masks do not provide any protection.”

That's just not in line with what we do know. Mask technology isn't new. This seems overly broad as well, how did they account for say hand washing? Everyone had the same hand washing regime? I doubt they controlled for that.

Here's the thing, if you don't trust in the level of masks. You are completely free to do better. This isn't an argument to go backwards in protection.

https://www.acpjournals.org/doi/10.7326/M20-6817

From the study: Inconclusive results, missing data, variable adherence, patient-reported findings on home tests, no blinding, and no assessment of whether masks could decrease disease transmission from mask wearers to others.

The article doesn't say when this was carried out. Was it when there were few active cases[1]. If this was carried out during the time with few active cases it would be like testing an umbrella by walking around with it open on a day with a low chance of rain. Doesn't do a good job of testing the umbrella.

There is other research showing better protection like that at Beaumont health system[2]. This was in environments with varying levels of exposures (including nurses treating COVID patients).

I wish there were more details.

[1] https://www.worldometers.info/coronavirus/country/denmark/

[2] https://www.freep.com/story/news/health/2020/11/16/beaumont-...

Masks are about reducing the spread of the virus to other people, not about protecting the wearer.

Is this something we have missed are there other studies that found the opposite?

(1) https://www.acpjournals.org/doi/10.7326/M20-2671

Studies comparing populations with almost 100% mask wearing and countries with almost no masks would make for a better comparison.