Can you help me understand the clinical significance of slowing the spread of COVID from 0.76% to 0.67% (< 0.1% absolute risk reduction) with surgical masks? It's nice to finally have a cluster RCT on masks. But even in a well-done high quality study, a statistically significant finding may not translate to clinical significance and advisable public policy? This study may show us that cloth masks don't provide benefit. But what degree of benefit are surgical masks providing (which also needs to weighed against the potential clinical and societal "costs/harm" of masks)?
Fair pt. That delta however was only during the duration of the study, so both numbers (and the delta) may grow with time, but the more relevant q IMO is whether anyone would expect this effect size in highly vaccinated/ highly naturally immune communities. I think that is unknown.
Isn't the entire effect of surgical masks in the 50+ population? Can you explain how that mechanism works? It's actually much larger in the older population and is reduced by being totally ineffective in all groups under 50 isn't it?
Agreed! Those are more relevant questions. But to the layman, I worry they'll focus on the statement "surgical masks slowed the spread of COVID" without understanding the nuances of statistical significance vs. clinical significance and generalizably. It would be a shame to finally have some high-quality evidence on this heated topic and its findings used in a misleading manner.
Exactly. It's a poor trial design but some people want to say it proves something. As you have pointed out 0.1% reduction. That is within the margin of error. It's just noise, a rounding error. We are going to make public policy based on that? Good grief.
There is no clinical significance. Slowing spread ceases to have any relevance within the whole logical apparatus of "flattening the curve" to prevent the healthcare system from being "overwhelmed" once the herd immunity myth is dispensed with - if you slow spread during non-waves (including the observation period of this study), you just move cases backward in time - that doesn't mean they still won't happen simultaneously during the next wave, due to building up more immune debt. There's no point to slowing spread. It's superstitious nonsense.
I think it's very telling the only cluster RCT is out of....Bangladesh. We certainly have the resources to conduct more relevant data to our specific situation within the United States. I think taking the whole thing a step further; what should be the endpoint purpose of masks in regard to what many would consider an endemic virus? In other words does the small benefit of slowing the spread in a cloth mask, at a time when a vast majority are either vaccinated or have natural immunity - serve any real medical purpose in light of the fact we will all encounter this virus.
An 11.6% relative risk reduction for surgical masks isn't terribly compelling. There were a lot of covid like symptoms in both arms (surgical mask and no mask) of the trial with only an one (1) percent absolute risk reduction. So surgical masks aren't that great either....unless, I guess you don't know the difference between a rRR and an aRR.
Oh, please an rRR of 1.12 is pretty meaningless even in a RCT since there's obviously confounding with social distancing and possibly other factors. Namely was the group with masks more likely to social distance and take other precautions or not.
As for vaccines, plenty of confounding there as well with NPI's.... Plus read the actual FDA trials, the selection bias is pretty blatant. The trials were under powered for the people most at risk namely those over 75, and with multiple comorbidities. Moderna largely excluded people with more than one comorbidity. There were a total of 8 events between the two mRNA trials for people over 75 with neither trial having more than 4% of their trial in this age group despite 62% of deaths occurring in this cohort. Only 4% of Moderna's trial had more than 1 comorbidity. These trials were also with main white people and before any of the variants emerged. So the 90% numbers were more than a bit contrived.
Also still don't know why Pfizer didn't verify 3410 events as noted on p. 42 of their FDA report (1594 of those events were in the vaccinated arm of that trial). At least, JNJ was a bit more forthcoming, and did a better job of having a more representative demographics...though that's why they also had lower rRR's and for people over 60 with more than 1 comorbidity, the efficacy of their vaccines dropped from 72.9% to 42.3% .
So try reading the actual trials rather than the PR reports. It's really no surprise what's occurring in Israel (UK data as well). Those most at risk, vaccinated or not, are still getting sick and dying despite the disease immunity afforded by the vaccines.
I've already read the study, any way you want to spin it a 8.62% reduction in the control group down to a 7.62% in the masked arm isn't significant. There were similar numbers of covid like symptoms in both groups.- masked arm (N=13,273) and control arm (N=13,893) - that small difference relative to the total size of each arm may be due to a myriad of things.
As for your other links, yeah I've read that site...and what struck me more was that he didn't provide the aRR's which were very very small especially for under 60 age groups. Plus what I've found going through the data myself, is that basically old people unvaccinated people accounted for most of the deaths before vaccines were available, and old vaccinated people accounted for most of the deaths after the vaccines were available.... This was true of the Scottish data as well available for Public Health Scotland. See: https://beyondspin.wordpress.com/2021/09/28/problems-with-data/
From the Scottish data, the real world efficiencies for cases and hospitalizations were more in the 58 to 72% range ...though this includes AZ vaccinations as well.
Thanks for the laugh, but you can't extrapolate data like that...To assume you can do so is just plain silly, and shows you don't have a clue as to the relationship between aRR and rRR's. rRR's are ratios, so the denominators don't change the math that much. To illustrate what I mean, here are three hypothetical trials all with different N's.
Trial 1 (N= 10 & 10 in each arm)
3 cases in 10 = 0.3 = 30%
2 cases in 10 = 0.2 = 20%
rRR = (0.3 - 0.2)/0.3 = 33%
aRR = 10%
Trial 2 (N= 100 & 100)
3 cases in 100 = 0.03 = 3%
2 cases in 100 = 0.02 = 2%
rRR = (0.03- 0.02)/ 0.03 = 33%
aRR = 1%
Trial 3 (N= 1000 & 1000)
3 cases in 1000 = 0.003 = 0.3%
2 cases in 1000 = 0.002 = 0.2%
rRR = (0.003-0.002)/0.003 = 33%
aRR = 0.1%
All three have the same rRR's. All three have very different aRR's. You need to know both numbers to understand the significance of the rRR's. The aRR also gives you the NNT . The NNT for Trial 1 is 10, for Trial 2 is 100 and for Trial 3 it's 1000. So that's a huge difference between Trial 1 and Trial 3.
As for your second point, you're assuming that vaccines are the only determiner of severity of outcome. Whereas the reality is a bit more confounded. First, the variant may be less virulent even if more transmissible. More people getting infect under 50 means more cases with people less susceptible to adverse outcomes, And less deaths over 50, could mean many of the most susceptible people have already died. But still when most old people were unvaccinated, most old people died...just like now where most old people are vaccinated and most old people are still the one's dying. Why? Older people are more susceptible to adverse outcomes if infected.
It did in Bangladesh. My sentence was meant to say that it cannot help us estimate effect size here in USA in the present moment. But their primary endpoint was significant.
OK, been trying to wrap my head around this. Aren't the 95% confidence intervals tiny? Does this study tell us anything about the US if you can reject the lower bound but not the upper bound?
The intervention isn't really "masks" in comparison to no mask. They were primarily studying their whole program, which included education. And they found that their program not only increased mask wearing it ALSO increased social distancing.
That could be where the effect comes -- if the elderly are more capable of social distancing (less likely to work and if they do work, less likely to work at jobs where social distancing is impossible?).
If social distancing works, but cloth masks plus social distancing didn't work, that could suggest the same conclusion as the 2015 Vietnam cloth mask RCT that suggested cloth masks were actually detrimental.
What I want to know is what kind of cloth masks they used in the study. Surgical masks are all similar; cloth masks aren't. You go from single layer bandannas to multi layer cloth masks with a non-woven layer and even a pocket for an additional high end filter. And cloth masks can fit much better since sizing is easier. This study only shows that the cloth masks they used and anything lower quality are less effective. If they did the study with high grade 4 layer masks, well and good, cloth masks don't work. But if they did it with lower grade masks then my high end cloth masks might still work.
The observed "better" results for surgical masks could still be an indirect effect (in general, the study observed increased "distancing" in intervention villages; it could just be that surgical masks turned more people into hypochondriacs). Such an indirect, psychologically-derived impact would not translate to other cultures or economic contexts.
The results for elderly villagers in the surgical mask villages are especially spurious. How many people are actually over 60 years-old in rural Bangladesh? It seems like less than 10% of the population. Less than .1 of the population of 200 (surgical mask intervention) villages is too small for the statistical confidence the authors asserted.
Note that the study observation period wasn't even during a wave. They only collected blood samples from villagers who reported "symptoms" during household surveys, and there was no baseline seropositivity sampling, contra the author's own distorted text (it seems that "baseline" simply refers to seropositivity in week 1 survey respondents; but it's unclear).
And as commented by Hannah, to what end? What is the point of slowing transmission? It is a seasonal virus.
Thoughts on higher quality masks? It seems to make sense to only compare cloth to surgical when that was all that was available but if it’s now easier to get a KN95 or N95 should we evaluate those? And if they’re highly effective, and available, why not push for them? Sure, not everyone may want to wear an N95, but some of the KN95s are more comfortable and if the point is to actually limit spread…
A lot of KN95's are counterfeit. So also check out KF94 masks. These are the Korean government certified equivalent masks to N95 masks. KF94 mask are also readily available. Here's a good video https://youtu.be/WE5Uo3F2TdU on tests of some KF94 masks from a mechanical engineer who is into masks
Just another dude on the internet too much. but I'm beginning to go from a pro-mask stance to a perhaps we don't need them for kids < 12 stance. But with some of the anit-mask stuff I've seen, I think it misses a key point about what we know. Enclosed spaces lend themselves to a certain viral load gathering in the air. The fact the virus can slip through a mask doesn't address the rate at which an enclosed space becomes more infectious. As such, I still think promoting masks in such cases makes sense. In my head, adult lungs are potential pumps of transmission dense air in enclosed spaces. But children < 12, or vaccinated adults...perhaps that drops. Curious how others see it.
TBH, I'm almost scared to think what would the reaction be if everyone suddenly realized that masks likely do nothing for prolonged indoor exposure.
Half the country is still trying to minimize transmission hard. A lot of schools would go 100% remote if everyone realized that masks likely do little.
So, it's pushing for 100% science based policy, vs. letting people think that masks work so that at least most schools can stay open.
That's correct cloth and loose fitting surgical masks don't really do that much for stopping airborne aerosols so such low quality mask wearing is really just theater. Higher quality masks are more effective, but in schools, restaurants, bars, etc.... the emphasis should really be on air quality through better ventilation, filtration, uv lights and CO2 detectors.
These are good questions. The issue here is where the viral particles are. If they are in the <0.5um size range, they are like cigarette smoke and go either through or out the edges of most masks, and then hang in the air. IE wearing a mask doesn't reduce the airborne prevalence, primarily they would only work to reduce intake = the video on this tweet shows the effects of various masks on cigarette smoke as an example. (https://twitter.com/Emily_Burns_V/status/1398023020808134656)
That twitter thread which is informative, but long, banks on the thesis that something like 87% of the actually infectious viral particles are in the 0.3um size range and hence this demonstration is valid. I'm unable to tell you at this time if this thesis is correct, but if it is, then masks do almost nothing to stop transmission because, by design, they won't catch the right particles.
Thanks for the info. More questions though. Doesn't the virus need moisture to be able to transmit? That's why there was a delay to say it was an airborne disease? If the requirement for the particle is to be riding along with our breathing fluids is that part of the .3um size? I imagine masks are capturing a lot of the moisture of our breath.
It does not need significant amounts of moisture. You are correct in that masks are capturing the majority of the moisture, but there is separate evidence from influenza that getting a droplet based infection is correlated with better outcomes than an aerosol infection (obviously either can have minor and severe disease, but aerosol tends towards more severe and droplet towards less). The thesis is that inhaling the infectious agent into your lungs bypasses the mucus membranes - giving your body much less time to mount a defense before the virus is in it's primary grounds. So ironically, we might be better off getting hit by the moist air. I don't think there are corona studies on this, but the expectation is that it would be the same.
Though I don't agree with him on a lot of things, Dr. Michael Osterholm has been pretty good with masks pointing out how most transmission is via smaller airborne aerosols rather than larger droplets....and time (duration of exposure) is a factor. This is actually what most of the current science on respiratory viral transmission indicates...contrary to CDC guidance. See: https://www.pnas.org/content/118/17/e2018995118 and https://www.science.org/doi/10.1126/science.abd9149
So these aerosols go right through cloth masks and around loose fitting surgical masks. Higher quality masks like N95 and KF94 masks must fit tightly against one's face. So beards also reduce the effectiveness of masks. Here's a clip from Osterholm's podcast on masking:
Can you help me understand the clinical significance of slowing the spread of COVID from 0.76% to 0.67% (< 0.1% absolute risk reduction) with surgical masks? It's nice to finally have a cluster RCT on masks. But even in a well-done high quality study, a statistically significant finding may not translate to clinical significance and advisable public policy? This study may show us that cloth masks don't provide benefit. But what degree of benefit are surgical masks providing (which also needs to weighed against the potential clinical and societal "costs/harm" of masks)?
Fair pt. That delta however was only during the duration of the study, so both numbers (and the delta) may grow with time, but the more relevant q IMO is whether anyone would expect this effect size in highly vaccinated/ highly naturally immune communities. I think that is unknown.
Isn't the entire effect of surgical masks in the 50+ population? Can you explain how that mechanism works? It's actually much larger in the older population and is reduced by being totally ineffective in all groups under 50 isn't it?
The study didn’t look at cloth vs surgical vs no mask. It looked at their whole NORM protocol which included masks among other education.
They found that their protocol increased mask usage but also increase social distancing.
I suspect it increased the social distancing primarily in the older crowd and that was where the effect came from.
Agreed! Those are more relevant questions. But to the layman, I worry they'll focus on the statement "surgical masks slowed the spread of COVID" without understanding the nuances of statistical significance vs. clinical significance and generalizably. It would be a shame to finally have some high-quality evidence on this heated topic and its findings used in a misleading manner.
Exactly. It's a poor trial design but some people want to say it proves something. As you have pointed out 0.1% reduction. That is within the margin of error. It's just noise, a rounding error. We are going to make public policy based on that? Good grief.
Vinay you are smarter than this.
BINGO
There is no clinical significance. Slowing spread ceases to have any relevance within the whole logical apparatus of "flattening the curve" to prevent the healthcare system from being "overwhelmed" once the herd immunity myth is dispensed with - if you slow spread during non-waves (including the observation period of this study), you just move cases backward in time - that doesn't mean they still won't happen simultaneously during the next wave, due to building up more immune debt. There's no point to slowing spread. It's superstitious nonsense.
I think it's very telling the only cluster RCT is out of....Bangladesh. We certainly have the resources to conduct more relevant data to our specific situation within the United States. I think taking the whole thing a step further; what should be the endpoint purpose of masks in regard to what many would consider an endemic virus? In other words does the small benefit of slowing the spread in a cloth mask, at a time when a vast majority are either vaccinated or have natural immunity - serve any real medical purpose in light of the fact we will all encounter this virus.
An 11.6% relative risk reduction for surgical masks isn't terribly compelling. There were a lot of covid like symptoms in both arms (surgical mask and no mask) of the trial with only an one (1) percent absolute risk reduction. So surgical masks aren't that great either....unless, I guess you don't know the difference between a rRR and an aRR.
Doesn't the 11.6% risk reduction with a delta Sars-Cov2 with R0 > 3 mean you are just delaying the infection by a few hours (a day max at best) ?
Oh, please an rRR of 1.12 is pretty meaningless even in a RCT since there's obviously confounding with social distancing and possibly other factors. Namely was the group with masks more likely to social distance and take other precautions or not.
As for vaccines, plenty of confounding there as well with NPI's.... Plus read the actual FDA trials, the selection bias is pretty blatant. The trials were under powered for the people most at risk namely those over 75, and with multiple comorbidities. Moderna largely excluded people with more than one comorbidity. There were a total of 8 events between the two mRNA trials for people over 75 with neither trial having more than 4% of their trial in this age group despite 62% of deaths occurring in this cohort. Only 4% of Moderna's trial had more than 1 comorbidity. These trials were also with main white people and before any of the variants emerged. So the 90% numbers were more than a bit contrived.
Also still don't know why Pfizer didn't verify 3410 events as noted on p. 42 of their FDA report (1594 of those events were in the vaccinated arm of that trial). At least, JNJ was a bit more forthcoming, and did a better job of having a more representative demographics...though that's why they also had lower rRR's and for people over 60 with more than 1 comorbidity, the efficacy of their vaccines dropped from 72.9% to 42.3% .
So try reading the actual trials rather than the PR reports. It's really no surprise what's occurring in Israel (UK data as well). Those most at risk, vaccinated or not, are still getting sick and dying despite the disease immunity afforded by the vaccines.
I've already read the study, any way you want to spin it a 8.62% reduction in the control group down to a 7.62% in the masked arm isn't significant. There were similar numbers of covid like symptoms in both groups.- masked arm (N=13,273) and control arm (N=13,893) - that small difference relative to the total size of each arm may be due to a myriad of things.
As for your other links, yeah I've read that site...and what struck me more was that he didn't provide the aRR's which were very very small especially for under 60 age groups. Plus what I've found going through the data myself, is that basically old people unvaccinated people accounted for most of the deaths before vaccines were available, and old vaccinated people accounted for most of the deaths after the vaccines were available.... This was true of the Scottish data as well available for Public Health Scotland. See: https://beyondspin.wordpress.com/2021/09/28/problems-with-data/
From the Scottish data, the real world efficiencies for cases and hospitalizations were more in the 58 to 72% range ...though this includes AZ vaccinations as well.
#
Thanks for the laugh, but you can't extrapolate data like that...To assume you can do so is just plain silly, and shows you don't have a clue as to the relationship between aRR and rRR's. rRR's are ratios, so the denominators don't change the math that much. To illustrate what I mean, here are three hypothetical trials all with different N's.
Trial 1 (N= 10 & 10 in each arm)
3 cases in 10 = 0.3 = 30%
2 cases in 10 = 0.2 = 20%
rRR = (0.3 - 0.2)/0.3 = 33%
aRR = 10%
Trial 2 (N= 100 & 100)
3 cases in 100 = 0.03 = 3%
2 cases in 100 = 0.02 = 2%
rRR = (0.03- 0.02)/ 0.03 = 33%
aRR = 1%
Trial 3 (N= 1000 & 1000)
3 cases in 1000 = 0.003 = 0.3%
2 cases in 1000 = 0.002 = 0.2%
rRR = (0.003-0.002)/0.003 = 33%
aRR = 0.1%
All three have the same rRR's. All three have very different aRR's. You need to know both numbers to understand the significance of the rRR's. The aRR also gives you the NNT . The NNT for Trial 1 is 10, for Trial 2 is 100 and for Trial 3 it's 1000. So that's a huge difference between Trial 1 and Trial 3.
Read:
Relative risk versus absolute risk: one cannot be interpreted without the other https://academic.oup.com/ndt/article/32/suppl_2/ii13/3056571
As for your second point, you're assuming that vaccines are the only determiner of severity of outcome. Whereas the reality is a bit more confounded. First, the variant may be less virulent even if more transmissible. More people getting infect under 50 means more cases with people less susceptible to adverse outcomes, And less deaths over 50, could mean many of the most susceptible people have already died. But still when most old people were unvaccinated, most old people died...just like now where most old people are vaccinated and most old people are still the one's dying. Why? Older people are more susceptible to adverse outcomes if infected.
Get the facts from someone that is involved in trial designs. This is a must read. Please share. https://boriquagato.substack.com/p/bangladesh-mask-study-do-not-believe?utm_source=substack&utm_medium=email&utm_content=share&token=eyJ1c2VyX2lkIjoyODc5NTg3NywicG9zdF9pZCI6NDA3ODEzODcsIl8iOiJ2MTVrdyIsImlhdCI6MTYzMjc2MDI0NCwiZXhwIjoxNjMyNzYzODQ0LCJpc3MiOiJwdWItMzIzOTE0Iiwic3ViIjoicG9zdC1yZWFjdGlvbiJ9.l-k8JEhE_IjZRfvCN1LhtvYduvu67Y1FlW3GrYaxpSQ
If their trial does not help us estimate their effect size, can you really say "surgical masks slowed the spread of symptomatic SARS-CoV2?"
It did in Bangladesh. My sentence was meant to say that it cannot help us estimate effect size here in USA in the present moment. But their primary endpoint was significant.
OK, been trying to wrap my head around this. Aren't the 95% confidence intervals tiny? Does this study tell us anything about the US if you can reject the lower bound but not the upper bound?
Page 28
https://www.poverty-action.org/publication/impact-community-masking-covid-19-cluster-randomized-trial-bangladesh
Figure 3 in https://www.poverty-action.org/sites/default/files/publications/Mask_RCT____Symptomatic_Seropositivity_083121.pdf shows surgical masks providing significant infection reduction for 50 years and older but none for younger age brackets. This step function seems counter-intuitive to me. Shouldn't younger people, who naturally interact more in society, benefit more from higher quality NPI?
The intervention isn't really "masks" in comparison to no mask. They were primarily studying their whole program, which included education. And they found that their program not only increased mask wearing it ALSO increased social distancing.
That could be where the effect comes -- if the elderly are more capable of social distancing (less likely to work and if they do work, less likely to work at jobs where social distancing is impossible?).
If social distancing works, but cloth masks plus social distancing didn't work, that could suggest the same conclusion as the 2015 Vietnam cloth mask RCT that suggested cloth masks were actually detrimental.
That would explain the big differential. Thank you.
What I want to know is what kind of cloth masks they used in the study. Surgical masks are all similar; cloth masks aren't. You go from single layer bandannas to multi layer cloth masks with a non-woven layer and even a pocket for an additional high end filter. And cloth masks can fit much better since sizing is easier. This study only shows that the cloth masks they used and anything lower quality are less effective. If they did the study with high grade 4 layer masks, well and good, cloth masks don't work. But if they did it with lower grade masks then my high end cloth masks might still work.
The observed "better" results for surgical masks could still be an indirect effect (in general, the study observed increased "distancing" in intervention villages; it could just be that surgical masks turned more people into hypochondriacs). Such an indirect, psychologically-derived impact would not translate to other cultures or economic contexts.
The results for elderly villagers in the surgical mask villages are especially spurious. How many people are actually over 60 years-old in rural Bangladesh? It seems like less than 10% of the population. Less than .1 of the population of 200 (surgical mask intervention) villages is too small for the statistical confidence the authors asserted.
Note that the study observation period wasn't even during a wave. They only collected blood samples from villagers who reported "symptoms" during household surveys, and there was no baseline seropositivity sampling, contra the author's own distorted text (it seems that "baseline" simply refers to seropositivity in week 1 survey respondents; but it's unclear).
And as commented by Hannah, to what end? What is the point of slowing transmission? It is a seasonal virus.
Thoughts on higher quality masks? It seems to make sense to only compare cloth to surgical when that was all that was available but if it’s now easier to get a KN95 or N95 should we evaluate those? And if they’re highly effective, and available, why not push for them? Sure, not everyone may want to wear an N95, but some of the KN95s are more comfortable and if the point is to actually limit spread…
A lot of KN95's are counterfeit. So also check out KF94 masks. These are the Korean government certified equivalent masks to N95 masks. KF94 mask are also readily available. Here's a good video https://youtu.be/WE5Uo3F2TdU on tests of some KF94 masks from a mechanical engineer who is into masks
Just another dude on the internet too much. but I'm beginning to go from a pro-mask stance to a perhaps we don't need them for kids < 12 stance. But with some of the anit-mask stuff I've seen, I think it misses a key point about what we know. Enclosed spaces lend themselves to a certain viral load gathering in the air. The fact the virus can slip through a mask doesn't address the rate at which an enclosed space becomes more infectious. As such, I still think promoting masks in such cases makes sense. In my head, adult lungs are potential pumps of transmission dense air in enclosed spaces. But children < 12, or vaccinated adults...perhaps that drops. Curious how others see it.
TBH, I'm almost scared to think what would the reaction be if everyone suddenly realized that masks likely do nothing for prolonged indoor exposure.
Half the country is still trying to minimize transmission hard. A lot of schools would go 100% remote if everyone realized that masks likely do little.
So, it's pushing for 100% science based policy, vs. letting people think that masks work so that at least most schools can stay open.
That's correct cloth and loose fitting surgical masks don't really do that much for stopping airborne aerosols so such low quality mask wearing is really just theater. Higher quality masks are more effective, but in schools, restaurants, bars, etc.... the emphasis should really be on air quality through better ventilation, filtration, uv lights and CO2 detectors.
These are good questions. The issue here is where the viral particles are. If they are in the <0.5um size range, they are like cigarette smoke and go either through or out the edges of most masks, and then hang in the air. IE wearing a mask doesn't reduce the airborne prevalence, primarily they would only work to reduce intake = the video on this tweet shows the effects of various masks on cigarette smoke as an example. (https://twitter.com/Emily_Burns_V/status/1398023020808134656)
That twitter thread which is informative, but long, banks on the thesis that something like 87% of the actually infectious viral particles are in the 0.3um size range and hence this demonstration is valid. I'm unable to tell you at this time if this thesis is correct, but if it is, then masks do almost nothing to stop transmission because, by design, they won't catch the right particles.
Thanks for the info. More questions though. Doesn't the virus need moisture to be able to transmit? That's why there was a delay to say it was an airborne disease? If the requirement for the particle is to be riding along with our breathing fluids is that part of the .3um size? I imagine masks are capturing a lot of the moisture of our breath.
It does not need significant amounts of moisture. You are correct in that masks are capturing the majority of the moisture, but there is separate evidence from influenza that getting a droplet based infection is correlated with better outcomes than an aerosol infection (obviously either can have minor and severe disease, but aerosol tends towards more severe and droplet towards less). The thesis is that inhaling the infectious agent into your lungs bypasses the mucus membranes - giving your body much less time to mount a defense before the virus is in it's primary grounds. So ironically, we might be better off getting hit by the moist air. I don't think there are corona studies on this, but the expectation is that it would be the same.
Just reading through the Twitter thread now. Guess should have read that first. I'll lave this here though for others.
Though I don't agree with him on a lot of things, Dr. Michael Osterholm has been pretty good with masks pointing out how most transmission is via smaller airborne aerosols rather than larger droplets....and time (duration of exposure) is a factor. This is actually what most of the current science on respiratory viral transmission indicates...contrary to CDC guidance. See: https://www.pnas.org/content/118/17/e2018995118 and https://www.science.org/doi/10.1126/science.abd9149
So these aerosols go right through cloth masks and around loose fitting surgical masks. Higher quality masks like N95 and KF94 masks must fit tightly against one's face. So beards also reduce the effectiveness of masks. Here's a clip from Osterholm's podcast on masking:
https://youtu.be/0rY6Dezgt3s
Poor trial design, poor control, no baseline. It simply proves people are gullible. https://mail.google.com/mail/u/0/?tab=rm#search/bangla/WhctKKWxdNWvjjzQFwxMlPPNBbVDffJPFLxdGVgxfXJdHTLcVVxpFwzcmcCxdLcGzsDCqXB
Suspicious link
Here is the proper link. This should be a must read. https://boriquagato.substack.com/p/bangladesh-mask-study-do-not-believe?utm_source=substack&utm_medium=email&utm_content=share&token=eyJ1c2VyX2lkIjoyODc5NTg3NywicG9zdF9pZCI6NDA3ODEzODcsIl8iOiJ2MTVrdyIsImlhdCI6MTYzMjc2MDI0NCwiZXhwIjoxNjMyNzYzODQ0LCJpc3MiOiJwdWItMzIzOTE0Iiwic3ViIjoicG9zdC1yZWFjdGlvbiJ9.l-k8JEhE_IjZRfvCN1LhtvYduvu67Y1FlW3GrYaxpSQ