TLDR: To get the sort of protection people imagine that cloth masks provide, you would need to be wearing an n95 mask, tightly fitted to your face so no air leaks in through the sides.

https://www.pbs.org/wnet/amanpour-and-company/video/do-masks...

It doesn't have to personally protect you at high effectiveness from getting infected to reduce spread at a population level.

Even a 50% reduction in spread is huge in a population. Maybe we aren't getting that with masks, but it's not a binary "you are protected"/"you are not protected" problem.

>Needless to say, masking is political hot button beyond anything I've ever seen in public health.

At the same time i think we've all done a disservice to the public.

When you actually look at face cloth coverings, they actually only have very limited impact in reducing the amount of virus that you inhale in or exhale out.

Studies that have been done show that if an individual might get infected within 15 minutes in a room, by time and concentration of the virus in the room, add a face cloth covering you only get about five more minutes of protection.

I've been really disappointed with my colleagues in public health for not being more clear about what can masking can do or not do.

On the other hand if you use the n95 respirators and fit them tight to your face, you can actually spend 25 hours in that same room and still be protected.

The bottom line though is by telling people that in fact just putting a face cloth covering on is going to protect you is simply not true.

https://www.pbs.org/wnet/amanpour-and-company/video/do-masks...

Cloth masks are nowhere near good enough protection to allow children too young to be vaccinated to return to school.

I'm just asking if we have info on population spread effects for masks / no masks.

"Masks won't protect you" isn't an answer to that question. I don't wear a mask when requested by local guidelines or businesses as some kind of guarantee that I don't get COVID.

And yes, having kids not all go to school and then return to their families on a daily basis would probably have a much bigger affect on community spread. But if we can't get political will for masks or vaccinations then I don't know where we're going to find it for another round of kids staying home.

The answer to the question is that cloth masks are effective against viruses with a droplet based spread, but not against a fully airborne virus.

Note that cloth masks almost completely did away with last year's Flu season, while we were right in the middle of a huge Covid surge.

NEW YORK (AP) — February is usually the peak of flu season, with doctors’ offices and hospitals packed with suffering patients. But not this year.

Nationally, “this is the lowest flu season we’ve had on record,” according to a surveillance system that is about 25 years old, said Lynnette Brammer of the U.S. Centers for Disease Control and Prevention.

https://apnews.com/article/flu-has-disappeared-us-pandemic-2...

https://www.king5.com/article/news/health/coronavirus/zero-f...

A 50% reduction and we still all get covid. It is actually binary -- either we have a realistic and obtainable plan for zero-covid (which we do not) or everyone gets exposed to covid eventually.

A 50% reduction in spread might be helpful in certain areas where the hospitals are on the verge of being overwhelmed (in which case just close the schools for a few weeks), but in the United States there are a lot of mask mandates in schools being pushed in areas where the hospitals are not under any significant pressure. That is nonsense.

Sure in an ideal world as soon as hospitalizations or case rates went above some metric we'd introduce stricter local procedures, hopefully fast enough that the wave of hospitalizations 1-2 weeks later isn't too bad.

But so far it seems like we're too slow on that. Things get bad, then we start changing our behavior. Time matters and it's not binary. That's been the whole principle of managing this thing in the US at the beginning. If you let the spike get too big too quickly then it gets bad before we can take corrective action.

And how would we even manage changing these guidelines on a week-by-week basis in every zip code? How do you even disseminate that information to all businesses, citizens, parents?

Of course I don't think all restrictions make sense in all places, nor do I want them to go on forever. Vaccinations for a large majority of eligible individuals would go a long way to reducing spread and hospitalization load.

In theory we are trying to bide time until we get there (manageable COVID, not zero COVID) but in the US at least we're not heading towards "large majority" very quickly, and we are still having those exponential local spikes.

Probably pretty close to zero when we’re talking about being in a classroom with 30 other kids for a few hours. The mask protects against things going straight ahead, not against slowly filling up a room with aerosols.

I guess masking up might mean everyone gets slowly infected over the course of days though (through aerosols), instead of getting a full dose of virus straight in the face. I presume that affects the severity of the subsequent disease.

I appreciate the simplicity of the message to mask up, since it’s almost certainly better than nothing, but it’s no panacea.

The likelihood that a cloth mask can do that in a classroom however…

Best mitigator would be good HEPA room air purifiers, ideally multiple per classroom.

They can be too loud to run while class is in session, especially if they move enough air to be worth a damn. Double-especially if you're also masked (so speaking is already a bit muffled).

There is no "best" here, mitigations all mitigate different things and work together to provide a safer environment.

Where do you think the extra air goes?

It still makes it into the air, just in different directions. Some of the viral particles are probably caught in the mask, but I’m not sure how much of the total we can count on.

Specifically, anything that covers your mouth.

If we had enough N95 masks to give to everyone (and they’d actually wear them) we could stop the virus within a few weeks :P

Hell, just switching to surgical masks would make a ton of difference.

Edit: Allow me to clarify - the research everyone is citing that says masking is effective in teachers and ineffective in students (the 37% number) predates both the delta variant and widespread infection in Southern states. Further, masking is understood etiologically as a prevention method and has been used successfully in other outbreaks and in other countries. Clinicians and policy makers as a rule work with incomplete data in an emerging situation, so unequivocally stating that masking kids in schools doesn't help is a very bad misrepresentation of both the data/research and the implications to policy.

My understanding was that masks were primarily effective at preventing high viral load droplets from spreading the virus during short interactions.

I don't have any source to prove that to be the case because data on the effectiveness of masks seems frustratingly sparse.

We may not have trials or studies (these things take time) to back a very certain and/or specific claim such as "do masks prevent the spread of Covid 19?" What we do have, is fundamental knowledge and common sense and so typically, in a clinical setting we ask these questions when any new situation arises (as it happens often in medicine):

- Does this reccomendation cause more harm than good?

- is there even a slight chance that this clinical decision would increase the percentage chance of survival?

- is it worth the inconvenience it could cause?

This is called Clinical Reasoning. Thinking critically and clinically is a core tenet of the field.

"Research shoes masks are still effective even when spending the whole day in the same room"

I'm not aware of any evidence that this is the case and I worry that people are putting too much stake in masks when really social distancing is much more effective than masks ever will be.

This is a common attribute of infections and is really more of a math issue than anything SARS-specific. The bigger the initial dose, the sooner it will get to the impact stage, and the less prepared your immune system will be at that time.

https://www.nature.com/articles/s41598-020-72798-7 It does note that non-medical (e.g. cloth) masks may be less effective, but whether those are used a lot seems to depend on environment (nobody seems to use them here). Edit: One more for cloth masks https://www.nature.com/articles/jes201642

Key paragraph: Between Nov. 16 and Dec. 11, researchers found that infection rates were 37% lower in schools where teachers and staff members were required to wear masks. The difference between schools that did and did not require students to wear masks was not statistically significant.

A good recent article in NY Mag also discussing this issue, including the fact that the World Health Organization recommends against masking kids under six: https://nymag.com/intelligencer/2021/08/the-science-of-maski...

Many countries in Europe have decided against masking for any students in K-12 schools because it is unclear that the harms outweigh the benefits. The idea there is some "simple" scientific & research consensus on this is wrong.

Is it worth the cost? That’s a different question.

I’m not really opposed to masks in a classroom as a mitigation method, but if people believe it will significantly alter the trajectory of the infections I have a bridge to sell them.