5 ms·

Mask mandate and use efficacy for Covid-19 containment in US States

17 points by mrfusion 5y ago

space_fountain 5y ago
I'm not equipped to evaluate, but a quick Google seems to suggest this result is against the majority of other papers. That's not to say it's wrong, just that reading most other papers on the subject would suggest something else
- criticaltinker 5y ago
  Per the OP: > Higher self-reported mask use protected against SARS-CoV-1 in Beijing residents [30], but RCTs found no differences in PCR confirmed influenza among Hong Kong households assigned to hand hygiene with or without masks [mask use 31% and 49%, respectively] [31]. Medical and cloth masks did not reduce viral respiratory infections among clinicians in Vietnam [9] or China [10], and rhinovirus transmission increased among universally masked Hong Kong students and teachers in 2020 compared with prior years [32]. These findings are consistent with a 2020 CDC meta-analysis [33] and a 2020 Cochrane review update. Care to cite the literature you're reading that contradicts these statements? I'm genuinely interested in learning more about the state of scientific consensus on this topic.
  - manwe150 5y ago
    Not directly in reply to your question, but an anecdote I thought might be relevant: I was recently reading more about Ignàc Semmelweis, the doctor famous for promoting hand washing. He was finding that hand washing had almost no impact on the outcomes in a particular hospital. He eventually discovered that they needed to wash the sheets better too. Either intervention alone would have almost no impact, but together they were powerful. Source: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(04)16022-4/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
  - space_fountain 5y ago
    I was mostly responding to this statement > We did not observe association between mask mandates or use and reduced COVID-19 spread in US states. COVID-19 mitigation requires further research and use of existing efficacious strategies, most notably vaccination. Googling turns up lots of articles like this: * https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0252315 https://journals.plos.org/plosone/article?id=10.1371/journal... * https://www.cdc.gov/mmwr/volumes/70/wr/mm7010e3.htm https://www.cdc.gov/mmwr/volumes/70/wr/mm7010e3.htm The statements made seem compatible, but I think reading just this article you could come away thinking mask mandates are a bad idea. They might be, but a quick google does make that seem more doubtful. As another commenter pointed out the impact is probably pretty small though and easily swamped by other factors. Who is better controlling for those factors isn't something that's clear to me. Covid also isn't the flu so I'm not sure how relevant masks effectiveness against the flu is to covid. I think influenza has a lot more surface transmission than covid for example
- manwe150 5y ago
  I think it is also known that the signal is weak, since there are so many other unknown factors, and that makes it hard to discern from the noise (or perhaps easy to cherry-pick results). So it is possibly still an open question of whether has an impact in the short/medium/long term, whether it requires better compliance levels, or whether it simply does no harm to wear them. It seems that the measurement problem is difficult without challenge trials, and it is unclear how that could be done blinded nor even ethically.
criticaltinker 5y ago
> Our main finding is that mask mandates and use likely did not affect COVID-19 case growth. Mask mandates were associated with greater mask use but ultimately did not influence total normalized cases or post-mandate case growth. > we did not observe lower growth rates over a range of compliance at maximum Fall-Winter growth [45-83% between South Dakota and Massachusetts during maxima] when growth rates were high. This complements a Danish RCT from 3 April to 2 June 2020, when growth rates were low, which found no association between mask use and lower COVID-19 rates either for all participants in the masked arm [47% strong compliance] or for strongly compliant participants only. > We only assessed one biological quantity [confirmed and probable COVID-19], but the ongoing pandemic warrants assessment of other factors such as hospitalizations and mortality. Importantly, our study does not disprove the efficacy of all masks in limited and controlled circumstances, such as properly worn N95 respirators. It's important to be aware that mandated non-pharmaceutical interventions like lock-downs, school closures, - and to a lesser degree masking - have second order effects on seasonal endemic illnesses such as influenza and RSV. Large future outbreaks of both diseases may occur following a period of extended NPIs. These outbreaks, which may reach peak numbers in the winter, could increase the burden to healthcare systems [1]. Considering these potential consequences, and the other potential negative externalities mentioned in the paper, it's imperative that such mandates be carefully scrutinized and evaluated before being widely enforced. [1] The impact of COVID-19 nonpharmaceutical interventions on the future dynamics of endemic infections https://www.pnas.org/content/117/48/30547 https://www.pnas.org/content/117/48/30547
- charbonneau 5y ago
  I'm not sure why parent is getting downvoted. What's wrong about having the opinion that mandates should be "carefully scrutinized and evaluated before being widely enforced"? You do not have to hold that view. You are free to criticize it. But downvoting seems counterproductive to any reasonable discussion. As one HN'er put it: > The downvote button is not a disagree button. If you disagree with something, add your own comment. That's the point of a discussion board. Downvotes are for comments which are not worthy of a response because they are not honest attempts at discussion. https://news.ycombinator.com/item?id=23998406 https://news.ycombinator.com/item?id=23998406
vannevar 5y ago
As I understand it, this study concludes that their index of mask use (based on the University of Washington's IHME data) correlates with infection minima, but not the maxima. In other words, a higher rate of mask use helps keep COVID-19 levels low when they are low, but doesn't seem to slow them down when infection rates rise. There's overwhelming evidence that mask use is effective in retarding the spread of COVID-19 (e.g., https://jamanetwork.com/journals/jama/fullarticle/2776536 https://jamanetwork.com/journals/jama/fullarticle/2776536, https://science.sciencemag.org/content/372/6549/1439 https://science.sciencemag.org/content/372/6549/1439, and many others). So I suspect that what's happening here is that mask use keeps the rates low among the masked, but once the infection rate takes off among the unmasked, there are enough vulnerable individuals to render the pool effectively infinite from the virus's point of view, and the number of masked individuals becomes irrelevant since they have no effect on the large, vulnerable unmasked pool.
- vannevar 5y ago
  Would the downvoters care to share their perspective, and/or evidence to the contrary?
  - mikem170 5y ago
    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.

17 points by mrfusion 5y ago

I'm not equipped to evaluate, but a quick Google seems to suggest this result is against the majority of other papers. That's not to say it's wrong, just that reading most other papers on the subject would suggest something else

criticaltinker 5y ago
Per the OP: > Higher self-reported mask use protected against SARS-CoV-1 in Beijing residents [30], but RCTs found no differences in PCR confirmed influenza among Hong Kong households assigned to hand hygiene with or without masks [mask use 31% and 49%, respectively] [31]. Medical and cloth masks did not reduce viral respiratory infections among clinicians in Vietnam [9] or China [10], and rhinovirus transmission increased among universally masked Hong Kong students and teachers in 2020 compared with prior years [32]. These findings are consistent with a 2020 CDC meta-analysis [33] and a 2020 Cochrane review update. Care to cite the literature you're reading that contradicts these statements? I'm genuinely interested in learning more about the state of scientific consensus on this topic.
- manwe150 5y ago
  Not directly in reply to your question, but an anecdote I thought might be relevant: I was recently reading more about Ignàc Semmelweis, the doctor famous for promoting hand washing. He was finding that hand washing had almost no impact on the outcomes in a particular hospital. He eventually discovered that they needed to wash the sheets better too. Either intervention alone would have almost no impact, but together they were powerful. Source: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(04)16022-4/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
- space_fountain 5y ago
  I was mostly responding to this statement > We did not observe association between mask mandates or use and reduced COVID-19 spread in US states. COVID-19 mitigation requires further research and use of existing efficacious strategies, most notably vaccination. Googling turns up lots of articles like this: * https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0252315 https://journals.plos.org/plosone/article?id=10.1371/journal... * https://www.cdc.gov/mmwr/volumes/70/wr/mm7010e3.htm https://www.cdc.gov/mmwr/volumes/70/wr/mm7010e3.htm The statements made seem compatible, but I think reading just this article you could come away thinking mask mandates are a bad idea. They might be, but a quick google does make that seem more doubtful. As another commenter pointed out the impact is probably pretty small though and easily swamped by other factors. Who is better controlling for those factors isn't something that's clear to me. Covid also isn't the flu so I'm not sure how relevant masks effectiveness against the flu is to covid. I think influenza has a lot more surface transmission than covid for example
manwe150 5y ago
I think it is also known that the signal is weak, since there are so many other unknown factors, and that makes it hard to discern from the noise (or perhaps easy to cherry-pick results). So it is possibly still an open question of whether has an impact in the short/medium/long term, whether it requires better compliance levels, or whether it simply does no harm to wear them. It seems that the measurement problem is difficult without challenge trials, and it is unclear how that could be done blinded nor even ethically.

criticaltinker 5y ago

> Our main finding is that mask mandates and use likely did not affect COVID-19 case growth. Mask mandates were associated with greater mask use but ultimately did not influence total normalized cases or post-mandate case growth. > we did not observe lower growth rates over a range of compliance at maximum Fall-Winter growth [45-83% between South Dakota and Massachusetts during maxima] when growth rates were high. This complements a Danish RCT from 3 April to 2 June 2020, when growth rates were low, which found no association between mask use and lower COVID-19 rates either for all participants in the masked arm [47% strong compliance] or for strongly compliant participants only. > We only assessed one biological quantity [confirmed and probable COVID-19], but the ongoing pandemic warrants assessment of other factors such as hospitalizations and mortality. Importantly, our study does not disprove the efficacy of all masks in limited and controlled circumstances, such as properly worn N95 respirators. It's important to be aware that mandated non-pharmaceutical interventions like lock-downs, school closures, - and to a lesser degree masking - have second order effects on seasonal endemic illnesses such as influenza and RSV. Large future outbreaks of both diseases may occur following a period of extended NPIs. These outbreaks, which may reach peak numbers in the winter, could increase the burden to healthcare systems [1]. Considering these potential consequences, and the other potential negative externalities mentioned in the paper, it's imperative that such mandates be carefully scrutinized and evaluated before being widely enforced. [1] The impact of COVID-19 nonpharmaceutical interventions on the future dynamics of endemic infections https://www.pnas.org/content/117/48/30547 https://www.pnas.org/content/117/48/30547

charbonneau 5y ago
I'm not sure why parent is getting downvoted. What's wrong about having the opinion that mandates should be "carefully scrutinized and evaluated before being widely enforced"? You do not have to hold that view. You are free to criticize it. But downvoting seems counterproductive to any reasonable discussion. As one HN'er put it: > The downvote button is not a disagree button. If you disagree with something, add your own comment. That's the point of a discussion board. Downvotes are for comments which are not worthy of a response because they are not honest attempts at discussion. https://news.ycombinator.com/item?id=23998406 https://news.ycombinator.com/item?id=23998406

vannevar 5y ago

As I understand it, this study concludes that their index of mask use (based on the University of Washington's IHME data) correlates with infection minima, but not the maxima. In other words, a higher rate of mask use helps keep COVID-19 levels low when they are low, but doesn't seem to slow them down when infection rates rise. There's overwhelming evidence that mask use is effective in retarding the spread of COVID-19 (e.g., https://jamanetwork.com/journals/jama/fullarticle/2776536 https://jamanetwork.com/journals/jama/fullarticle/2776536, https://science.sciencemag.org/content/372/6549/1439 https://science.sciencemag.org/content/372/6549/1439, and many others). So I suspect that what's happening here is that mask use keeps the rates low among the masked, but once the infection rate takes off among the unmasked, there are enough vulnerable individuals to render the pool effectively infinite from the virus's point of view, and the number of masked individuals becomes irrelevant since they have no effect on the large, vulnerable unmasked pool.

vannevar 5y ago
Would the downvoters care to share their perspective, and/or evidence to the contrary?
- mikem170 5y ago
  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.