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> There's overwhelming evidence that mask use is effective in retarding the spread of COVID-19 It's probably not fair to phrase it as overwhelming evidence. Ye

> There's overwhelming evidence that mask use is effective in retarding the spread of COVID-19 It's probably not fair to phrase it as overwhelming evidence. Yes there is evidence that masks can reduce transmission, and the citations you provided included a fair amount of research supporting this idea (thanks for those references). And just thinking about it logically, it seems obvious masks would have such an effect. However the evidence presented in OP - and the previous studies it cited - provide counter-evidence suggesting that mask usage and mandates may not have a significant beneficial impact on the overall course of a pandemic. There are a variety of possible reasons for this, which you began to speculate on. Poor compliance, people not wearing their masks correctly, porous cloth masks, poorly ventilated indoor environments contributing to high viral load environments even with 100% mask compliance - the number of places where things can go wrong are tremendous and it begs the question of if the tradeoffs of mask mandates are worth it, or if our resources would be better spent on other viral elimination strategies.

vannevar 5y ago
I should probably rephrase that as overwhelming evidence that they are effective in a clinical setting---ie, in a lab, and in medical settings. The point is, if you're sitting in a room with an infected person, there have been many studies that show that you will get a lower exposure if you're masked, and a much lower exposure if the infected person is masked as well. I posted a more detailed explanation of my theory above. You don't need to account for imperfections in masks, or ventilation, or any other details. Even if you make the assumption that masks are perfectly effective, the observations seen by the researchers might be explained by exponentially increasing spread among the unmasked. To use an analogy, a 4' child can drown just as easily in a 5' deep pool as in 100' deep lake. The percentage of mask usage referenced in the paper would only dictate the depth of the pool, so it's not surprising it would have little effect once the virus takes hold in the unmasked population. Barring very high mask usage (making the pool only 2' deep, to continue the analogy), exponential infection spikes in the unmasked population are unavoidable. It doesn't mean masks don't work, it only indicates just how high usage needs to be to stop these spikes.

vannevar 5y ago

I should probably rephrase that as overwhelming evidence that they are effective in a clinical setting---ie, in a lab, and in medical settings. The point is, if you're sitting in a room with an infected person, there have been many studies that show that you will get a lower exposure if you're masked, and a much lower exposure if the infected person is masked as well. I posted a more detailed explanation of my theory above. You don't need to account for imperfections in masks, or ventilation, or any other details. Even if you make the assumption that masks are perfectly effective, the observations seen by the researchers might be explained by exponentially increasing spread among the unmasked. To use an analogy, a 4' child can drown just as easily in a 5' deep pool as in 100' deep lake. The percentage of mask usage referenced in the paper would only dictate the depth of the pool, so it's not surprising it would have little effect once the virus takes hold in the unmasked population. Barring very high mask usage (making the pool only 2' deep, to continue the analogy), exponential infection spikes in the unmasked population are unavoidable. It doesn't mean masks don't work, it only indicates just how high usage needs to be to stop these spikes.