Do you have a dumb question that you're kind of embarrassed to ask in the main thread? Is there something you're just not sure about?
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Notes -
I don't buy it. Everyone was wearing masks everywhere for two years and everyone still got Covid.
There's certainly no high-quality evidence that masks work, and that's remarkable considering just how hard they were being pushed.
But let's consider another possibility. What if large scale mask wearing actually increases disease burden? It's not just a binary of works/doesn't work. It's a trinary of works/doesn't work/is harmful.
Wearing masks is one of those things that only works some of the time and probably don't scale all that well. Different illnesses spread easier/harder to start with; COVID was so prolific, considering how naive everyone's immune system was, that masks hardly put a dent it in. Concerning scaling, preventing disease transmission takes a fair amount of effort, and simply throwing a mask on while continuing to do everything that you would have otherwise done is definitely not going to cut it at scale.
But of course masks can and do help reduce the spread of disease if used diligently and in conjunction with other efforts. My family got together, all in one house, for a couple weeks around Thanksgiving. My sister showed up sick (not COVID; she had bought the plane ticket months in advance), and my mom is immunocompromised. My sister mostly isolated herself in a bedroom (working from home) and wore a mask whenever she came out until she got over it. My mom also put on a mask when she was likely to be in the same room as my sister for a nontrivial amount of time. Thankfully, no one else caught whatever she had.
Is this actually why most of the people that you're seeing in public have masks? Almost certainly not. But it probably does explain some percentage. Would be difficult to find out what percentage that is.
"masks" (or at least the ones everyone wears) do not stop or slow the spread of respiratory diseases; I wouldn't be surprised if something like a P100 respirator had some effect on respiratory illnesses, but as far as I know this isn't studied and certainly not at scale
if they "of course" did, it would be easy to find a strong statistically significant effect and yet when people try to do that they don't find it unless the "study" is helplessly compromised and manipulated
the best studies do not find this effect; the most they can do is find a weak effect which is washed out by any number of intentional or unintentional issues with the study themselves
Your "COVID is the only thing that matters" or "I only discovered this topic because of COVID" bias is showing. You do know that you can search Google Scholar for pre-2019 papers, right? Example
covid isn't the only respiratory disease and non-covid illnesses are included in this cochrane review of physical interventions to reduce the spread of respiratory viruses which includes quite a few papers from before 2019, e.g., the exact paper you're linking in your comment
I guess it's a good thing the selected group to conduct the review knows about google scholar
You know that you can search for pre-2019 papers, right? Citing a post-COVID review is likely shot through with motivation, one way or the other. In any event, that funnel plot looks pretty funnel-y, in the direction of a small benefit. Not surprising, given the wide array of different situations/interventions/adherence that they're having to muddle through in this type of meta-review. My position is vastly smaller in scope and cannot be dismissed by simply citing such a large agglomerating meta-review. Masks/quarantining/such can have a small effect of reducing risks in small, discrete settings. That is saying nothing about widespread use, which is rife with all sorts of weird interactions, adherence effects, etc. We don't have to say anything about that mess of a problem to be able to say, "If your sister is sick, do you think you're more likely to catch the disease from her if you both just stay at your respective houses all week, or if she comes over and sleeps in your bed with you all week?" We don't need to say anything about that big mess of a problem to say, "If your sick sister comes over for a few hours, does wearing a mask for the short period of time and washing hands help your probability a little bit over hugging and kissing?"
The Cochrane review is nice because it lists a large bulk of articles, even excluded ones, which are cited for easy reading if you're inclined.
I'm sure there is motivation, for e.g., the main author on the paper you linked has received grants and worked as as consultant for 3M corporation, the largest maker of masks in the United States at the time. Did you know that? Did that make you think the paper was "shot through with motivation"?
Lucky for us, the list has other papers with the listed outcomes for you to look at which are pre-2019 and you can read them past the abstract.
this tends to happen when the passable positive studies find weak evidence of weak effects
when you're at the point when you're relying on a bundle of unseparated actions to make an "but of course ___" statement about any particular one let alone trying to pass off as a fair comparison masks vs kissing each other, you're at best just over your skis
in any case, thanks for the dialogue
Congrats! We agree!
and if we just ignore the larger group which found no effects, let alone account for noise even in the passable positive studies, it would be an easier question to answer
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What do you mean by "evidence that masks work"?
Surely there's no meaningful doubt that COVID-19 is caused by SARS-CoV-2 virus particles, primarily entering through the nose and mouth, and the chance of infection increases with the number of virus particles (likely saturating at some point). Nor that N95+ or equivalent masks block the vast majority of such particles. Similarly, we also are pretty sure at this point that telling a population "wear a mask" has minimal public health benefits, since I hope we can agree that masks have no effect when not worn. To me, the non-obvious parts seem to be:
My big problem is almost noone wears N95. They wear nearly useless paper masks.
Wracking my brain, I recall a worker at Home Depot who wears an N95 and it looks properly fitted, not that you can truly tell by looking. Pretty much every other masker isn't wearing an N95.
Interesting. That's definitely different from my observations. I rarely see paper masks outside of medical offices (some of which still give them away and require masking) where they are definitely the most common type of mask. But elsewhere, I think KN95s are, although N95s aren't far behind. The rest are ones I just can't identify, which may be useless cloth masks, or the occasional paper mask. I'm occasionally tempted to straight-up walk up to those people and ask them (while I'm wearing my N95) why they are wearing an uncomfortable ineffective mask when there's no mandate, but I've never done so. (I don't think I've ever seen an airgami or P100 in the wild, although I've seen friends use them.)
(Of course, the vast majority of people I encounter in public outside of masks-required situations aren't wearing any mask at all; I'm not trying to imply mask wearing is at all common.)
My local distribution:
Almost everyone: no mask.
Most maskers: paper or cloth.
The select few elite amongst the maskers: N95.
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I admit that properly worn masks should work in a controlled situation. Like, if you really need to not get Covid right now, and you're on a bus full of infected, a properly worn N-95 should reduce your risk. Although I don't think this has really been studied, it seems fairly obvious that it should work.
Could masks make things worse for those who wear them? It certainly seems so.
What's the effect of trying to sterilize your environment to eliminate all exposure to antigens? For children, we know that this can be very negative. For adults, I believe it is likely negative as well. Other human systems thrive on adaptation to small amounts of stress. People who don't exercise are fragile. Is there a need to exercise your immune system as well? Probably.
Secondly, there could be a negative effect to mouth breathing your own stale air every day. The book Breath by James Nestor references a study where people's noses are blocked, forcing them to breath through their mouth. There are immediate and large negative health effects. Certainly no one would suggest wearing a mask 24/7. But even 8 hours a day seems likely to cause problems.
Do I have any evidence for this? No. I am pointing out that it's plausible that masks could do harm. It's not a case of good/nothing. It's a case of good/nothing/bad. We do have to consider the possibility that they cause harm. The evidence does suggest that they don't have any effect on a population level, which is why they were never recommended prior to Covid.
Is there a circumstance where I would I wear a mask? Actually, yes! If I thought I could entirely avoid a deadly disease I would do it. If, however, the disease were mild and inevitable, (as is Covid), wearing a mask would seem to do more harm than good. I am constantly in contact with Covid positive people, I go to crowded areas all the time, I never wear a mask, and I never get boosters. I got Covid just the one time in January 2022 and my immune system does the rest.
This is a complete misunderstanding of the hygiene hypothesis. I acknowledge that our understanding of the immune system remains pretty limited, but we are pretty certain that getting sick is bad for you.
And that seems like a reasonable trade-off to me. I have no interest in most activities that involve being around a lot of strangers where masking wouldn't work (e.g. bars/clubs/concerts), and I trust my friends I do spend time with unmasked to isolate when sick and be honest about exposures, so it doesn't cost me anything to wear a mask as I go about my normal daily life and it reduces my chance of infection to basically nothing. But I understand most people like gatherings with strangers, so the tiny marginal protection from, say, masking on the bus to/from such gatherings, is completely irrelevant to them. Just trying to explain why there's a minority for which masking is rational.
My understanding is not so much that getting sick is bad for you but rather that sickness occurs when your innate and specific immune systems are unable to stop/manage the replication of a given microorganism within the body without broader measures (fever, inflammation, production of mucus).
In terms of whether that is long-term bad, some sicknesses are indeed debilitating, and if one could achieve the same net outcome with less severe symptoms then it would clearly be preferable to do so. This is what happens with live accentuated vaccines in particular- a very mild illness (possibly subclinical) occurs that trains the specific immune system to recognise a feature of the attenuated pathogen common to the actual disease, resulting in reduced or eliminated illness when the actual disease is encountered.
I think the point is that this process occurs on a much broader scale on a daily basis as one travels through life. You are constantly exposed to microbes, and you can think of the body using mild or non- illness generating microbes of the same type as the training set for its response to novel (i.e. new to the body) pathogens. More data and more similar data= better response to a new pathogen.
The risk of actively trying to reduce illness by avoiding social contact and wearing a mask is that you are successful and your immune system "drifts" out of sync with the rest of the population. This is due to a reduced training set meaning that more pathogens are novel to the body.
If this occurs, then novel pathogens that would not harm the broader population due to previous exposures to them or related microbes still harm you because you have missed that exposure. The resulting illness will consequently be more severe because you have no cross-immunity, and so your immune system is effectively starting from scratch in its response.
You might object that the whole point is to avoid any airborne pathogen through masking and thus no risk of illness actually arises. However, a) you still have some social contact and thus disease vector and b) the countermeasures are only risk reduction not elimination. As your immune system drifts, then the range of potential pathogens increases as you lose cross-immunity. You therefore have the a lower absolute risk of being exposed to a given microbe, but the relative risk in the event of exposure is greater.
At the most extreme, uncontacted tribes have immune systems highly adapted to their limited social circle and environment: and no immunity against common circulating pathogens that generally cause mild illness such as influenza. This is not due to intrinsic immune differences between them and the rest of humanity, but rather a consequence of limited exposure.
Hope that explains why one might not wish to "mask up". I've not got into whether masks result in lower initial pathogen counts (and if so whether this is practically advantageous) or the broader effectiveness or social desirability of masks.
I do not expect that masking or isolation, even taken to an extreme, will cause any notable negative health effects due to your immune system getting "out of sync".
That might apply if you were being raised in a clean-room since birth, but as far as I'm aware, in situations such as an immigrant from the Global South going to the West, you don't see them suddenly falling sick because of all the novel pathogens circulating in a country several continents away. International travel at that range is not so common that I expect everything to become homogeneous when it comes to the short-scale evolution of pathogenic microbes. Note I am not claiming the opposite, it is both true and a trope that Western visitors to the Global South often catch stomach bugs because of exposure to pathogens that the locals are inured to, but that's more a factor of said pathogens being more common, be it because they flourish in tropical regions, or because of lax standards in food safety or water treatment.
I do not expect wearing a mask in public for even years on end to change anything, our innate immunity does a lot of the heavy lifting, the adaptive component, while not negligible, is hardly sufficient, as anyone going through flu season can tell you. We are also vaccinated for the worst diseases, and I'd expect maskers to be even more fastidious about getting their shots.
Uncontacted tribes do have differences in innate immunity. You can literally trace historical population exposure to diseases like the Bubonic Plague, Smallpox or Malaria through genetic adaptations. But someone in civilized society fastidious about masking is never going to be as vulnerable as them, once again unless they were raised in a clean room from birth. If there is a negative effect, it's too trivial to worry about.
On your comment on the differences in innate immunity in different human lineages, you're absolutely right and I was being imprecise in my wording. Mea culpa.
On the broader point, I think that you are potentially neglecting the common phenomenon of traveller's flu for the South to North traveller. People do get ill due to e.g. diffetences in circulating influenza strains. Agree that illness in the North to South traveller is more likely and severe due to the broader range and exposure to excitingly virulent pathogens.
You are of course right to say that the innate does a lot of the work, but for potential pathogens that can evade the initial response, then as you know a major factor in the severity of the illness (I.e length and how debiliating it is) is the existence of relevant B- or T- memory cells. My argument is that fewer relevant memory cells (etc) exist if you have experienced fewer relevant infections due to reduced exposure. Vaccines can close some but not all of the gap simply due to sheer range of potential pathogens.
Perhaps a relevant example would be a person from 1910 time travelling to 1925, at which point the Spanish Flu is still circulating. They would have a higher risk of dying from Spanish Flu than the average 1925 person because they do not have previous exposure to the strain itself, or to the various similar strains circulating post-1917 and generating relevant cross-reactions.
I think the only way masks work out for reducing severe illness long-term is if there is indeed a dose effect that results in exposure to the same pathogens but milder illness. If masks are so effective that one only gets ill vanishingly irregularly, then the risk of that occasional illness being severe are increased due to lack of relevant previous exposure. If masks are not effective at all such that one has a similar immune profile to the general population, then there is little point in wearing them.
I have never heard of Traveler's flu before, and as far as Google tells me, there's no clinically recognized condition by that name.
The closest I can find is this publication:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5505480/
I don't think this has much to do with traveling to a new place as much as it does with being crammed in tight spaces with poor ventilation with hundreds of others.
Similarly, if you travel to a new country during the flu season, you're at increased risk of catching it, but so are the locals. I am not aware of any literature claiming that new immigrants are at additional risk of catching flu and similar diseases, relative to the native population.
Masks vary greatly in terms of effectiveness, both from the specific type in question and proper use and adherence. But for a typical adult who begins masking in public, I do not expect that the the decreased exposure to pathogens will significantly impact their susceptibility to novel strains. In the case of the common cold or the flu, prior infection to a previous strain isn't protective for the next one that does the rounds, which is why flu vaccines are refreshed annual (and designed pre-emptively, based on models of what the next strain might be).
If someone masked and avoided the flu, for say, 2 years, I strongly doubt they are at any additional risk if they stop masking or catch the next one despite masking.
This is a different consideration from children, since I know that atopy is associated with insufficient exposure to a diverse array of microbes in childhood. Everything from peanut allergies to asthma can be mitigated by exposing them early and often. But for an adult, I do not expect it to make a difference.
Mind you, I don't disagree that wearing masks is largely pointless. Unless you're immunocompromised or are working with people who are, they are unlikely to help, unless maybe if you wear an N-95 on the plane and so on. What I disagree with is that they are meaningfully harmful on net to an average adult, which is a different question entirely from whether they provide benefits.
There are places, like China and Japan, where masking in public was common before the pandemic, and I have seen no claims that makes them more susceptible overall to respiratory illness when they do get it.
I think I disagree with the statement that various types of flu/colds do not generate any immunity: they simply fail to generate sufficient immunity to avoid symptomatic infection, which is why the new strains are able to circulate in the fairst place.
Now you can reasonably disagree that this cross-reactivity actually matters in terms of disease length/prognosis if you're still not immune enough to avoid getting ill, and I'm not sure whether it has been tested empirically. But it makes intuitive sense at least, and the principle seems to be accepted e.g. in this 2009 paper looking at swine flu immunity in the general population https://www.pnas.org/doi/abs/10.1073/pnas.0911580106
Overall, seems like a hard thing to study. Would be interesting if someone did an East/West study on whether flu is actually worse in the East due to reduced exposure (noting that it might still be less prelevant on the net due to effective masking). I would fall back on the statement that either masks are effective and decrease your exposure to disease and therefore your immunity relative to the unmasked population, or ineffective and therefore pointless.
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Yes, that's the "immune debt" hypothesis. It's a completely reasonable internally consistent hypothesis; it's not at all obvious that it's better to avoid infection entirely as opposed to hopefully getting minor infections that train the immune system while not being severe enough to do any lasting damage.
... but as far as I can tell, every vaguely reputable scientist with knowledge of the immune system or epidemiology thinks it is wrong and the odds don't work out that way.
To be clear, I'm merely claiming less exposure to pathogens is healthier. There are obviously costs to going out of your way to reduce your exposure to pathogens and the trade-off may not be worth it.
I'm not sure I share your views on whether immune debt is an unsupported position in the broader scientific community, but suspect that appealing to consensus may be unproductive.
Maybe the difference arises in the type of pathogen being discussed. A brief taxonomy could be the below:
I agree that you avoid (1) and (2) if possible.
For (3), it depends on the costs and consequences. Through the veil of ignorance, I personally think we opt for as high an exposure as possible to the extent this is typically mild. This can be via vaccinations or general exposure: to the extent that lower cost options such as vaccines are available, they should be taken, and the equation may change as technology moves ( for example a universal flu vaccine would negate the benefits of natural exposure).
For (4) I think you just take the mild cost.
So in this view, avoiding some pathogens is healthier, but for others it increases the effects of related pathogens so it is not healthier on the net.
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