4 ms·

Not a downvoter, but I'm sceptical of your conclusion. I took a look at the contents of the report, and it is denser than most. I was looking for some idea of

Not a downvoter, but I'm sceptical of your conclusion. I took a look at the contents of the report, and it is denser than most. I was looking for some idea of the magnitude of difference that you are seeing, and wasn't sure that I was looking in the right place. Beyond that I wonder what your premise amounts to. Waves of covid come and go in masked and unmasked states. What does it mean to say that masks slow growth at infection minima when a wave comes along and cases grow to a maxima despite the masks? I'm still chewing on this, but thought I'd throw this out there since you asked.

vannevar 5y ago
There are a lot of details in the paper, but the relevant conclusion is in the 'Results' section of the abstract: "Mask use predicted lower minimum but not lower maximum growth rates." The explanation that I offered is that, at low infection rates, people's probability of exposure is roughly the same whether or not they wear a mask, though their chance of infection is very different. This drags down the rate of infection proportionately to the number of masked people. Once the virus makes inroads in the unmasked community, however, the chance of an unmasked person getting exposed becomes steadily greater and greater, because an unmasked person is more likely to be around other unmasked people, which means that not only do they have a higher (relatively fixed) risk of being infected when exposed, they also have an increasingly high risk of being exposed. Then the exponentially increasing infections among the unmasked swamp the lower, relatively fixed rate at which the masked get infected.
- mikem170 5y ago
  But then why do masked populations end up with the same maximum growth rate? Doesn't that mean that mask populations end up catching it the same in the end? Wondering this, I wasn't sure of the significance of what you are saying. Also I wondered what is the magnitude of the different predicted lower minimum that the paper talks about is? i.e. 5% or 25% or 125%, etc. Some of those mask studies you linked to earlier were not great studies. I didn't click through everything, but for example the hairdresser study that one of them link to had no control (no hairdresser without a mask for comparison), confounding factors (hand hygiene compared to population, ventilation), and they didn't test all the customers (self reporting, also they didn't test customers from before the stylists developed symptoms (when they may have been at their most contagious). The USS Theodore Roosevelt study also mentioned had a lot going on, I wondered how they separated the self-reported mix of precautions (masks, social distancing, and common area avoidance), given the relatively small sample size for so many variables. I didn't look through the rest. On the other hand... Here's a randomized control trial covid mask study [0] involving 4800+ people that shows surgical mask wearing was not statistically significantly better than no mask. Here's another study [1] (pre-covid) involving 1600 people working in hospitals that shows cloth masks are penetrated by 97% of particles, compared to 44% for surgical masks. The authors of this study say that cloth masks may potentially increase infection risk, double masking making it worse (holding viruses particles near the face and moist breath). Another pre-covid paper [2] that analyzed 9 studies on medical/surgical masks (3500+ participants total) and concluded "wearing a mask may make little to no difference in how many people caught a flu‐like illness". I find the gap between what politicians and the media have been saying and these studies to be disturbing. But maybe this is why the CDC retracted their mask recommendation for vaccinated individuals several months ago, because the data doesn't show that masks help. [0] https://pubmed.ncbi.nlm.nih.gov/33205991/ https://pubmed.ncbi.nlm.nih.gov/33205991/ [1] https://www.researchgate.net/publication/275360639_A_cluster_randomised_trial_of_cloth_masks_compared_with_medical_masks_in_healthcare_workers https://www.researchgate.net/publication/275360639_A_cluster... [2] https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub5/full https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...
  - vannevar 5y ago
    >But then why do masked populations end up with the same maximum growth rate? There is no such thing in this study as a "masked population". The authors categorized the states based on the percentage of mask-wearers, according to the IHME data. But the reported infection rates don't distinguish between masked and unmasked. Your reference [0] looked at whether masks protect the wearer, and explicitly did not study whether masks on the infected protected others: "...no assessment of whether masks could decrease disease transmission from mask wearers to others." (From the Limitations section.) Your other references do not pertain to covid. The CDC changed their recommendation regarding masks for the vaccinated originally because they were satisfied that the vaccine provided sufficient coverage against serious illness to make unmasked, vaccinated individuals a very low public health risk. That changed when the Delta variant emerged and it became clear that vaccinated and infected individuals could spread the virus as readily as the unvaccinated infected, making them a potential vector and therefore a public health threat. As has been repeatedly reported, masks are primarily to keep the infected from infecting others, and again, there is a mountain of evidence that this is the case. As an aside, I upvoted your comment because even though I disagree, you presented an argument and provided references to support it.
    - mikem170 5y ago
      > As has been repeatedly reported, masks are primarily to keep the infected from infecting others, and again, there is a mountain of evidence that this is the case. I might not be seeing the same mountain of evidence that you are. The first couple studies I looked at in the metastudy you linked to in the original comment in this thread (hairdressers and navy ship) were not convincing (they were quite loose, as I commented on) and the second study you linked to seemed to assume that stopping droplets slows the spread, but doesn't offer evidence of how relevant stopping droplets actually is (there's data saying that covid spreads through aerosols just as well if not more than droplets [0], like in restaurants where people were not seated closely, etc.) I just don't see the effectiveness of cloth masks as proven. Where am I going wrong in my thinking? [0] https://www.sciencenews.org/article/covid-coronavirus-aerosol-droplets-airborne-evolution https://www.sciencenews.org/article/covid-coronavirus-aeroso...

vannevar 5y ago

There are a lot of details in the paper, but the relevant conclusion is in the 'Results' section of the abstract: "Mask use predicted lower minimum but not lower maximum growth rates." The explanation that I offered is that, at low infection rates, people's probability of exposure is roughly the same whether or not they wear a mask, though their chance of infection is very different. This drags down the rate of infection proportionately to the number of masked people. Once the virus makes inroads in the unmasked community, however, the chance of an unmasked person getting exposed becomes steadily greater and greater, because an unmasked person is more likely to be around other unmasked people, which means that not only do they have a higher (relatively fixed) risk of being infected when exposed, they also have an increasingly high risk of being exposed. Then the exponentially increasing infections among the unmasked swamp the lower, relatively fixed rate at which the masked get infected.

mikem170 5y ago
But then why do masked populations end up with the same maximum growth rate? Doesn't that mean that mask populations end up catching it the same in the end? Wondering this, I wasn't sure of the significance of what you are saying. Also I wondered what is the magnitude of the different predicted lower minimum that the paper talks about is? i.e. 5% or 25% or 125%, etc. Some of those mask studies you linked to earlier were not great studies. I didn't click through everything, but for example the hairdresser study that one of them link to had no control (no hairdresser without a mask for comparison), confounding factors (hand hygiene compared to population, ventilation), and they didn't test all the customers (self reporting, also they didn't test customers from before the stylists developed symptoms (when they may have been at their most contagious). The USS Theodore Roosevelt study also mentioned had a lot going on, I wondered how they separated the self-reported mix of precautions (masks, social distancing, and common area avoidance), given the relatively small sample size for so many variables. I didn't look through the rest. On the other hand... Here's a randomized control trial covid mask study [0] involving 4800+ people that shows surgical mask wearing was not statistically significantly better than no mask. Here's another study [1] (pre-covid) involving 1600 people working in hospitals that shows cloth masks are penetrated by 97% of particles, compared to 44% for surgical masks. The authors of this study say that cloth masks may potentially increase infection risk, double masking making it worse (holding viruses particles near the face and moist breath). Another pre-covid paper [2] that analyzed 9 studies on medical/surgical masks (3500+ participants total) and concluded "wearing a mask may make little to no difference in how many people caught a flu‐like illness". I find the gap between what politicians and the media have been saying and these studies to be disturbing. But maybe this is why the CDC retracted their mask recommendation for vaccinated individuals several months ago, because the data doesn't show that masks help. [0] https://pubmed.ncbi.nlm.nih.gov/33205991/ https://pubmed.ncbi.nlm.nih.gov/33205991/ [1] https://www.researchgate.net/publication/275360639_A_cluster_randomised_trial_of_cloth_masks_compared_with_medical_masks_in_healthcare_workers https://www.researchgate.net/publication/275360639_A_cluster... [2] https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub5/full https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...
- vannevar 5y ago
  >But then why do masked populations end up with the same maximum growth rate? There is no such thing in this study as a "masked population". The authors categorized the states based on the percentage of mask-wearers, according to the IHME data. But the reported infection rates don't distinguish between masked and unmasked. Your reference [0] looked at whether masks protect the wearer, and explicitly did not study whether masks on the infected protected others: "...no assessment of whether masks could decrease disease transmission from mask wearers to others." (From the Limitations section.) Your other references do not pertain to covid. The CDC changed their recommendation regarding masks for the vaccinated originally because they were satisfied that the vaccine provided sufficient coverage against serious illness to make unmasked, vaccinated individuals a very low public health risk. That changed when the Delta variant emerged and it became clear that vaccinated and infected individuals could spread the virus as readily as the unvaccinated infected, making them a potential vector and therefore a public health threat. As has been repeatedly reported, masks are primarily to keep the infected from infecting others, and again, there is a mountain of evidence that this is the case. As an aside, I upvoted your comment because even though I disagree, you presented an argument and provided references to support it.
  - mikem170 5y ago
    > As has been repeatedly reported, masks are primarily to keep the infected from infecting others, and again, there is a mountain of evidence that this is the case. I might not be seeing the same mountain of evidence that you are. The first couple studies I looked at in the metastudy you linked to in the original comment in this thread (hairdressers and navy ship) were not convincing (they were quite loose, as I commented on) and the second study you linked to seemed to assume that stopping droplets slows the spread, but doesn't offer evidence of how relevant stopping droplets actually is (there's data saying that covid spreads through aerosols just as well if not more than droplets [0], like in restaurants where people were not seated closely, etc.) I just don't see the effectiveness of cloth masks as proven. Where am I going wrong in my thinking? [0] https://www.sciencenews.org/article/covid-coronavirus-aerosol-droplets-airborne-evolution https://www.sciencenews.org/article/covid-coronavirus-aeroso...