So the only risk in life is Covid, there's no such thing as relative risk, masks could never be a net loss for anyone? No. Again, by all long-term studies, and with anti-correlation headwinds all over the place, mask mandates are not justified.
In the end, even a surgical mask will prevent e.g. the janitor from spitting on me for the 5m he comes by to check on things. If I'm wearing a FFP2, I'm also quite safe from aerosols, so it's a win, especially since maintaining distance is not something humans are reliably able to do.
Take this and multiply it by hundreds of situations and millions of people and you're bound to reduce contagion risk. I don't see why that's bad... especially since surgical masks are really cheap and not too inconvenient. Now if everyone were mandated to wear an FFP2 mask which is inconvenient maybe that would require more consideration.
Germany and USA: https://twitter.com/ianmSC/status/1359677558829191169
The clean fit to a face is pertinent to zero exposure. This is a common test in the military: dawn your mask, cover the vents, and suck in. If you don't feel immense pressure on your face, if you can't shake your head and do it again then you're metaphorically dead. Part of this fit is having a mask that fits your face and being clean shaven.
I don't know that COVID protection needs to hit this mark, since this is designed for nerve agents and nuclear fallout. It seems like trapping quantities of the virus is good enough, since it takes some threshold of exposure to get someone infected.
https://link.springer.com/article/10.1007/BF01658736
https://ncbi.nlm.nih.gov/pmc/articles/PMC2493952/pdf/annrcse...
for surprising null or even slightly negative result of surgeons masking vs. surgery patient wound infections.
Assuming linear scaling or other naive-model benefits from masks runs into large-scale gen-pop experience, which has now been studied by enough RCTs to cast doubt on the assumption. Long-term WHO and CDC policy guidance was based on empirical science showing non-pharmaceutical interventions are not very effective against respiratory viruses.
The fact that others are wearing surgical or even FFP2 masks is a protective bonus for me, even if the former vent or it doesn't protect them in all cases. I believe this was the reasoning of the German original fabric mask mandate starting spring/summer 2020: mask + no mask = 0, but mask + mask = good protection against droplets. Whether that made any significant difference with the transmission in aggregate is probably impossible to tell now, but it probably did prevent at least some infections. More importantly it made masks more normal, compared to spring where you were looked at like a maniac for wearing one.
Regarding the graph, Germany was and still is in a lockdown, so numbers will be going down masks or not. Upgrading the mandate to surgical/FFP2 was done more out of fear of the new mutations and it wasn't FFP2 only because it's economically / socially not tenable. I don't know why the US decreased, but the US is way ahead on vaccines and also had more infected, so I assume it will continue to do so.
1. It's not that hard for the general population to wear an FFP2 mask properly. I'm reasonably sure that this also applies to N95 masks. If you'll read the instructions that come with e.g. Dräger or Moldex masks, you'll see that the fitting procedure doesn't include anything as complicated as smell tests, but instructs the wearer to do a rather obvious leak test instead.
Dräger is now selling FFP2 masks directly to end customers: https://ffpshop.de/de/ffp-maske/draeger-x-plore-1720-ffp2-ma.... Check out the instructions, it's nothing fancy.
2. There are studies that indicate that surgical masks reduce risk even at population level. I've referenced them in a previous comment - https://news.ycombinator.com/item?id=25479729.
The conclusion of was "Any type of general mask use is likely to decrease viral exposure and infection risk on a population level, in spite of imperfect fit and imperfect adherence, personal respirators providing most protection. Masks worn by patients may not offer as great a degree of protection against aerosol transmission."
Finally, I'd like to address the RCT you've linked to from Denmark which I found interesting, but not particularly consequential. For me the biggest concerns are that:
* many things were self-reported.
* previous studies have found massive differences in wearer protection for surgical masks. Did they get a crap batch from China? It's not clear to me how they used masks. I can't reconcile 1.7 masks per weekday with the idea that such a mask should not be worn for more than a couple of hours or until it gets wet and the typical shift duration of 8h.
* didn't look at disease severity (or maybe I missed it?)
* didn't (couldn't) look at source control. For an individual it's important that they don't get sick (FFP2 preferred), for a government it's important that not too many people get sick (anything preferred, as long as it reduces transmission, even if it makes the wearer sick).