UMD study: N95 masks nearly perfect at blocking Covid
today.umd.edu
today.umd.edu
I'm always baffled by the people who went around arguing masks did nothing. They don't seem to have any problem accepting that a sneeze guard at a salad bar does something, or that a surgeon should put something on their face to prevent them from coughing into your open body cavity.
We can argue all day about specific masks under specific settings, or when it is worth it to bother, but "putting something in front of your face prevents you from breathing out particles" is in the category of "things that are pretty f&%*ing obvious".
https://newrepublic.com/post/175706/cassidy-hutchinson-trump...
It was never about science, it was about convenience.
There was an inverse problem coming from the other side though. There was also a large and vocal group who argued that the masks did nothing as a way to create unnecessary anxiety and force unnecessarily inconvenient lockdown restrictions - like banning people with "inferior" masks.
Not getting COVID in the first place seems like a huge benefit, and if you find yourself surrounded by people who no longer mask (most countries in 2024), then wearing an N95 respirator for your own protection is more personally beneficial compared to, say, being up to date on vaccination (since COVID vaccines don't prevent transmission, and repeated infections increase chances of acquiring long COVID).
I've consistently worn an N95 in all public spaces and have not contracted COVID (to my knowledge). Meanwhile, most of the people I know (some vaccinated, some not) are either often sick due to weakened immune systems and/or have gained one or more severe health issues since the pandemic began.
It was about less-educated people who were in arrested development and never moved past teenager rebellion. Their rebellion was egged on by malicious state actors through social media in order to sow large-scale chaos by unmitigated viral spread.
Here's someone specifically espousing the theory: https://www.cbc.ca/news/politics/covid-coronavirus-russia-ch...
> China is trying to rewrite the narrative, he said, by suggesting that U.S. army officers brought the virus to Wuhan during military games in December — but Kremlin-controlled media outlets appear to be trying to prolong the pandemic outside of Russia.
> "We saw articles ... claiming that handwashing has no impact on stemming the spread of the virus, that smokers do not get coronavirus, that ginger can be used to prevent contracting the disease," said Nehring. "Tons of false information that's never been corrected, never been retracted and is still online today, being put out by the Russians."
Kneecapping a geopolitical enemy by spreading disinformation would hardly be a first.
Russia pays for massive botfarms doing... something.
China funds massive social media investments into western markets for... something.
The topics don't even have to be relevant to anything geopolitical. As an example, the East Palestine train derailment was a weeks old news story that the Chinese media pushed into social media as a response to their balloon being shot down: https://www.bbc.com/news/world-asia-china-64633990
I mean clearly some types of masks are better than others, that's why there's standards for masks in the first place. This shouldn't be controversial. Worse by making it controversial the whole notion of doubting any kind of mask no matter how ill designed suddenly became a faux-pass. Severely obstructing any debate on the best way to make masks.
Heck as the article points out surgical masks (not designed to prevent infection from respiratory disease) only block around 70%. Chances are some people now want to shout how 70% is still a lot but 70% fewer particles is a whole lot different from a 70% lower chance of infection.
We could all have cooperated to figure out the best way to make masks, but somehow the debate was so heavily leaning towards whether masks were at all effective (which as you pointed out is really fucking obvious), that any notion of debating which masks were most effective and in which contexts was interpreted as a way to delegitimize masks as whole.
Edit: And really the lazy attempts to cast doubt on the effectiveness of masks should have been recognized as disingenuous. The idea that no masks work is easily dismissed because we've been testing and designing masks for all kinds of purposes for ages, so at best it is an argument for a higher class of mask, never no mask at all.
Except...
I would stake my fortune that the difference between 70% effectiveness and 99% effectiveness in a monitored study is going to be reduced into a rounding error in the real world. There are so many factors to control for when it comes to how they get used, how good they fit, how much they trap moisture over a long day, how much their performance degrades, etc.
For the purpose of preventing most incidental exposures, I would think that at the end of the day anything that prevents direct airflow is going to perform practically the same.
In my case, I was exclusively using N95s when I caught Covid back in the day, and it was probably for a myriad of ways that I was using the mask wrong or making other bad choices. The mask itself being 99% effective probably didn't significantly change my odds when I had to wear it 14 hours a day.
Frankly I don't know, and I don't mind admitting I don't know. What worries me greatly though is that at some point saying you didn't know was misconstrued as an attack on ideology.
I mean if I had to guess I'd go for something blocking 99% of the viruses at least 70% of the time over something blocking 70% of the particles at least 99% of the time. Of course it depends, but one of those works to some extent at least 70% of the time, while for the other it is unclear.
But really it depends. If we're talking about umbrellas those two scenarios result in you getting roughly equally wet, yet if we're talking about bullet proof shields I'd take my chances with the shield stopping most bullets at least some of the time over the one stopping only 2 out of 3 bullets.
As a physician, I had a hard time understanding the ferocity with which some of my colleagues defended the "science" of masking when the Cochrane review(s) -- largely held to be the pinnacle of evidence-based-medicine -- were so underwhelming. I never had a problem with people arguing for them based on face validity (hehe), personal preference, that they "might" help, were "better than nothing," or any number of softer reasons.
Don't get me wrong -- as a physician I wore an N95 every shift, because I believe that the odds that they might help were much greater than the odds that they might harm. (And because my hospital's N95s are much more comfortable for me than our surgical masks, and other trivial reasons.)
But I had a hard time finding other physicians who were both steadfastly convinced of the incredible benefits of masking and also had taken any time to try to find or read the available literature on the topic.
https://www.cochrane.org/news/featured-review-physical-inter...
> Medical or surgical masks > > Seven studies took place in the community, and two studies in healthcare workers. Compared with wearing no mask, wearing a mask may make little to no difference in how many people caught a flu-like illness (9 studies; 3507 people); and probably makes no difference in how many people have flu confirmed by a laboratory test (6 studies; 3005 people). Unwanted effects were rarely reported, but included discomfort. > > N95/P2 respirators > > Four studies were in healthcare workers, and one small study was in the community. Compared with wearing medical or surgical masks, wearing N95/P2 respirators probably makes little to no difference in how many people have confirmed flu (5 studies; 8407 people); and may make little to no difference in how many people catch a flu-like illness (5 studies; 8407 people) or respiratory illness (3 studies; 7799 people). Unwanted effects were not well reported; discomfort was mentioned.
"The study's lead author, Tom Jefferson of the University of Oxford, promoted the misleading interpretation. When asked about different kinds of masks, including N95s, he declared, “Makes no difference—none of it.” In another interview, he called mask mandates scientifically baseless."
When the main author is misleading about the conclusions of his own report, you have to wonder how good his work was.
But if you want just arguments over data rather than doubting Jefferson on a personal basis, this paper[1] makes a compelling argument that the RCTs in the Cochrane review itself are good enough to make the argument masking works. GAVI has also a good answer to Cochrane[2].
[0] https://archive.ph/FlApv [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10484132/ [2] https://www.gavi.org/vaccineswork/yes-masks-reduce-risk-spre...
I would consider the article you're referencing less than mediocre. "The Cochrane review didn't show what we expected it would show because their standards are too high." They are not conflating "absence of evidence" -- readers are.
I think it's odd how often people reference the Bangladesh study as evidence supporting masks, apparently without having read it.
Ultimately, I think masks probably do have a statistically significant benefit. I also think that if the rigorous studies (yes, I mean mostly RCTs) to date have been underpowered to show this benefit, that the effect size is likely to be small enough to make the costs of bickering potentially nullify those benefits.
I still wear an N95 every shift.
UK NHS had regarded surgical masks to be ineffective for virus transmission prevention, after several studies, before the field politization in 2020
> They don't seem to have any problem accepting that a sneeze guard at a salad bar does something...
We just find disgusting other people saliva/touching our food. So we didn't accept that before 2020, but maybe we do now
> ...or that a surgeon should put something on their face to prevent them from coughing into your open body cavity
No doctor/nurse would use any kind of mask at the hospital, 90% of the time, before 2020
So not obvious
Compare this with: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...
which states "The pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks."
Anyone have a good insight on which has a more accurate methodology?
FWIW, I've been of the opinion that masks help (obviously they do something), so I'm inclined to doubt the link I gave above.
Cochrane's analysis is that they can't say if masks are effective or not. It's not evidence of harm or helpfulness. A similar way to think about this is if I show you a coin and ask you if it's weighted? You don't have enough information to make a determination (perhaps if I flip it a bunch of times you can claim one way but that's not part of the question/data). I didn't run any statistical analysis on their tables but given that their "Viral respiratory illness ‐ influenza/COVID‐like illness" for No Masks is 160/1000 while "Viral respiratory illness ‐ influenza‐like illness" for Masks is 50/1000 I'm guessing masks do have an effect but the amount of samples in their data is not enough to demonstrate it.
Where the oranges come from is the UMD paper is studying how many viruses appear in a plague doctor's mask [1] which is obviously different than how many individuals get sick (apples).
[1]: https://sph.umd.edu/sites/default/files/styles/optimized/pub...
> The use of a N95/P2 respirators compared to medical/surgical masks probably makes little or no difference for the objective and more precise outcome of laboratory‐confirmed influenza infection (RR 1.10, 95% CI 0.90 to 1.34; 5 trials, 8407 participants; moderate‐certainty evidence).
More surprising is that cloth masks were better than KN95s! That's pretty cool. Sample size was quite small though (only 8 cloth mask participants) and the study in general had a pretty small sample size (surely it couldn't have been difficult to find covid-positive individuals?).
Unfortunately the initiave was a (many)day(s) late, and $1(00000000) short. Other nations [that used a higher standard of mask] did not have nearly as bad of numbers as the US had under the mask usage policies/regulations.
Except N95 masks weren't designed for that at all. N95s and better masks have been worn for decades to protect the wearer from all kinds of airborne problems, from dust to virus particles. They have proven quite effective at that task. But maybe you think all those workers in the Ebola ward are just wearing masks as a fashion statement?
Masks do prevent the wearer from getting sick, far more than wearing no mask at all. Is it 100% protection? No, but nobody should be complaining about that. I'll take 95% protection or even 50% protection over no protection at all.
Wearing one properly isn't rocket science, but is non-obvious. There's an instruction sheet in the box. You put it on, and then, using your palms, squeeze the part over your nose, which bends the mask and the metal stiffener. Check that you got it right by exhaling, then take a deep breath and feel the edges of the mask pushing against your face. If you don't feel the mask pushing, you did it wrong. Training video from OSHA: [1]
There's a serial number on the box. If you type it into 3M's web site, they will tell you if it's valid and if anyone ever queried that number before. This protects against counterfeit masks. Once you get an OK from the site, initial the box, so you don't ask the site again.
There's also a test kit you can buy, with a little bottle of a strong-smelling substance. If you can smell it with the mask on, you did it wrong.
The way these things work is subtle. There's an inner layer that's an electret, with a permanent electric field. Particles smaller than the mask mesh are caught and held by the electric charge. That's what makes these work against really small particles. They're actually more effective as particles get smaller. The "95%" is for the particle size for which they are least effective.
I've been wearing those since the beginning of COVID and never got COVID. I had a supply of those, because I used to use a water jet cutter at TechShop. This is all ordinary personal protective equipment, familiar to anyone who works around moderately dangerous industrial processes.
I've been wearing the 3M 8210 N95 masks when indoors with other people and I have avoided getting sick at all for 4.5 years. Before covid lockdowns, I would get sick at least 5 times a year and the only thing that changed was wearing the mask when in higher risk situations.
Yes, they do.
> But the main purpose is to stop sick people spreading.
No, the main purpose of an N95 mask is definitely to protect the wearer first and foremost. It's why they were created and sold in the first place. These masks were intended to protect people from all manner of workplace environmental hazards, and they've been used for that for decades.
>And it’s more effective at preventing spread than preventing contraction.
Citation needed.
Also, many people purposely choose not to wear a mask during a pandemic, so a mask not worn is not protecting anyone. Protecting myself from people without masks is 100% the purpose of wearing an N95 mask. We aren't talking about cloth masks in this thread, this study was about N95 masks - the two are different in that a cloth mask protects others more than it protects the wearer, but an N95 mask will protect the wearer more than others (who may not be wearing any mask).
N95 masks to prevent you getting covid don’t help anymore than surgical when we know it was be contracted through skin and eyes etc.
If you’re wearing it in a workshop or some dusty place then obviously they are far superior to surgical masks as they are designed for the wearer.
And obviously wearing an N95 when you’re sick is more helpful than a surgical mask as they are much better fitting and don’t let as much through if you sneeze of cough.
This entire thread is about N95 masks.
>when we know it was be contracted through skin
Citation needed (you still didn't provide the previous citation I requested)
Yes, it can be contracted through eyes, so eye protection is another mitigation that helps. When I had to travel in 2021, we wore eye protection on the plane, as well as P100 masks. We were well protected and did not get sick.
>If you’re wearing it in a workshop or some dusty place then obviously they are far superior to surgical masks as they are designed for the wearer.
Guess what they wear in Ebola wards. Guess why they wear them.
As to COVID, dunno.
But feel free to double-check that one. Everything surrounding Covid is so tied to politics and identity, it's easy to get things mixed up between actual studies that have actually demonstrated a thing and people just spouting off whatever just came out of their assholes.
In other words, I believe I read an article on how we know now that Covid doesn't need droplets to transmit, but it honestly could have just been someone saying that there was an article claiming that and I've just conflated being told there's an article with actually reading the thing.
However, it doesn't matter how good the N95 material is if the virus travels on a water droplet _around_ the mask. This is what all the comments about fit means.
I only looked into it informally during the early pandemic, so recollection is a bit hazy. But IIRC different amounts of virus travel on different sized droplets. Different sized droplets also can have different behaviors. Big enough and it doesn’t get through the mask. I think there’s also a “small enough” point where they don’t penetrate very well because they basically bounce around with brownian-like motion, don’t really create much flow. Also, IIRC larger droplets carry more viral load, but I’m pretty sure the smaller ones stay suspended in the air longer.
It is a pretty complex space I think.
No it wasn't. It was "I don't want to wear one"[1]. And the frame of the argument was fit to the desire. It was true then and remains true now that the single best protection for You Personally (absent isolation) is to put on and wear a mask. That remains true whether or not the "fit" is ideal or on the state of "longterm wear habits" of the rest of society.
[1] Though eventually the politically reframed corrolary of "You can't make me wear one" got more play.
I think your cynicism is not supported by the study.
Also let's be really precise here. I'm not conflating anything and i think you don't realize you are.
1) KN95 and N95 use similar filter materials they both have to filter 95% of particles down to 3 microns, the difference is to do with certification N95 is a US certification and KN95 is a Chinese certification. So the material is essentially the same between them. The fits tend to be different.
2) What i'm getting at is the title said all N95s, that's not what the study found, it found that a specific fit style "duckbill" was "Nearly Perfect at Blocking COVID" the non duckbills did not.
So to be accurate what the study did NOT find which the title suggests is that all US certified masks that filter 95% of particles down to 3 microns were nearly perfect at blocking COVID.
> (To reflect the general public's use of masks, study volunteers were not fit-tested for their masks or trained how to properly wear them.)
Everything was moot though if you ripped off the mask and wiped your hands all over your face when you were done.
No, probably not. There's very little evidence of transmission via surface contact; you have to breathe a significant amount into the nose/lungs, and the surgical and N95 masks are additionally statically charged to keep viral particles stuck to them; this is how they block viruses much smaller than their own pores. (https://www.wired.com/story/the-physics-of-the-n95-face-mask...)
Though to your point it was probably a lower risk than what might have been implied.
I was surprised that the airlines were repeatedly trying to get people to remove their masks one time I flew on the tail end of the epidemic. Will they bring me chicken soup if I get sick?
Basically, if you are in a vulnerable group, wear a mask around others. Make it a good mask. Fit it well. Especially if the group is known to be 'risky' or large. And for those extremely vulnerable groups, wear a mask around them as a courtesy.
But it got warped into 'wear a mask around everyone at all times'. And that just didn't make sense to a lot of people.
That was never the message.
Inside your own home with your own family? No, nobody suggested that anyone must wear a mask in that situation.
Out in public, indoors, during high transmission times? Yes, absolutely wear a mask in that situation, every single time.
This is common sense stuff, but people fail at common sense quite often these days.
Thing is, at those times, responsibility needs to shift back to the individual to take care of themselves.
Most people judged they didn’t need substantial protection (else they’d have worn better masks, well fitted, always).
We sometimes look at human behaviour and find it superficially irrational. But this is an example where rationality simply doesn’t conform to what some would wish it to.
It’s still rational. And I would also argue it is common sense.
No, that isn't common sense at all. It's the opposite of common sense. Yes, you, yourself wearing a mask "budges the dial" ever so slightly. And the people in the house next to you wearing masks when appropriate also "budge the dial" just a tiny bit more. And thousands of others that wear masks "budge the dial" - well that dial is now spinning. That's how these things work. It's a group effort. But if the group is filled with morons that "think for themselves" (aka selfish assholes) then the dial will grind slower, because everyone's in it for themselves and don't believe that their actions have any effect on anyone else, which is pretty dumb.
>Thing is, at those times, responsibility needs to shift back to the individual to take care of themselves.
Yes, take care of your self. Wear the mask. Don't get sick so that you can't pass the sickness on to others. It's really that simple.
>Most people judged they didn’t need substantial protection
Think about the most average person you know. Half the people in the world are dumber than that. Most people are fucking stupid.
There's nothing rational about not wearing a mask in high risk situation during a global pandemic.
That’s basically my point. The group is already behaving as you describe. (Else transmission wouldn’t be high already.)
It’s OK to bemoan it. But it’s not reasonable to expect people to behave in a way that ignores reality on the ground.
> Most people are fucking stupid.
No, I don’t believe that. I can get on board with a criticism that many behaviours are automatic, and we are not always making conscious decisions. But in general, people are not stupid.
> There's nothing rational about not wearing a mask in high risk situation […]
It can readily be rationalised, but on the basis that it’s not actually a high risk situation.
* Not quite the same thing as "true". Very rarely paradigms are wrong. But they aren't here, and... I mean duh.
Masks work great at blocking transmissions even if the fit is bad, much like covering your mouse when you sneeze.
Masks CAN work great at blocking absorption if fitted properly, but thats hard to do correctly
If you are a fundamentally selfish person you only care about whether masks prevent YOU from getting COVID, you don't care about spreading it.
If you are non-selfish, then you probably care about both yourself and the broader community well being and are not only concerned about catching covid yourself, but also spreading covid to other people.
I think its hard for these two groups to interact because there's not much common ground.
I would argue that if you only care about your own risk of catching COVID and don't have training on N95 masks, then the argument that masks aren't worth the hassle is probably right.
> “Data from our study suggests that a mildly symptomatic person with COVID-19 who is not wearing a mask exhales a little over two infectious doses per hour says first author Jianyu Lai, a postdoctoral researcher at the PHAB Lab. “But when wearing an N95 mask, the risk goes down exponentially.”
I'm most baffled by the people I see today with a mask on but around their chin. They haven't been required for years, so I presume it's being particularly COVID-conscious (as someone on an immune suppressant, I still wear N95s in public)... but if you're that conscious you'd think you'd wear it right.
Maybe I've been thinking about this forum too highly for too long already? Probably.
Could this be another potential signal for the trend of the attention economy's created culture taking over in this turbulent and in many ways regressive global state?
If so, this is starting to feel "on rails". Scary.
Moderation has some huge blind spots that's allowed a corrosive element to build a core in the community. But that's the fate of all social networks. We've yet to figure out how to scale social interaction. When a network gets large enough to grant relative anonymity to people, the worst comes out.