5 ms·

This isn't a study; it is a mathematical model [1]. > Here, we develop a quantitative model of airborne virus exposure that can explain these contrasting resul

• dmead 5y ago
  you really had that list ready to go...
• chrischattin 5y ago
  Yeah, this right here. Masks efficacy for stopping viral transmission has been heavily studied. I could post literally hundreds more examples of statistically significant, RCT'd science showing they have no effect on viral transmission. Wearing masks has never been about the science.
  • oasisbob 5y ago
    > I could post literally hundreds more examples of statistically significant, RCT'd science showing they have no effect on viral transmission. Please do. I'm only aware of about a half-dozen controlled trials of mask usage, and they're all low-powered.
    • chrischattin 5y ago
      Here's a meta-study of 10 you can peruse... "In pooled analysis, we found no significant reduction in influenza transmission with the use of face masks (RR 0.78, 95% CI 0.51–1.20; I2 = 30%, p = 0.25)" https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article
• oarfish 5y ago
  Interesting how some of the linked studies either contradict your statement, or seem to have nothing to do with it.
  • brobdingnagians 5y ago
    Some are indirectly related, but all are linked in some way. Like how some find that it _could_ have a positive effect and postulate how, but that the studies they reviewed in the meta-review didn't _show_ that.
• takeda 5y ago
  The study about mask being ineffective is about cloth mask. That's why the hospital masks are no longer made of cloth.
  • brobdingnagians 5y ago
    That is true; but a large number of people are walking around with cloth masks believing that they are helpful, while that study has shown them to potentially increase risk. It did show "Penetration of cloth masks by particles was almost 97% and medical masks 44%." So that was a positive for medical masks. Though some of the other studies address how those need to be used properly and not re-used. The main point is that, in general, media has not done a good job of transmitting studies on risk reduction; they've mainly done propaganda, which can do more harm by promoting things like cloth masks and not informing people about proper use of medical masks.
    • tripletao 5y ago
      The Vietnamese study found that cloth masks increased risk compared to medical masks, not compared to no mask. Confusingly, their control group also wore masks, just in fewer situations: > Hospital wards were randomised to: medical masks, cloth masks or a control group (usual practice, which included mask wearing). The first paper doesn't say what kind of mask the control participants wore, but a subsequent paper says only 38/458 control participants wore a cloth mask. I think the implication is that the rest wore medical masks, though neither paper ever says explicitly. https://bmjopen.bmj.com/content/10/9/e042045 https://bmjopen.bmj.com/content/10/9/e042045 That subsequent paper is a subgroup analysis that should be treated with some care, but found comparable performance between medical masks and cloth masks washed in the hospital laundry. That suggests the problem was inadequate hand-washing, not the masks themselves. There is zero evidence that masks increase incidence of disease compared to no mask. RCTs of mask use in public (e.g., DANMASK-19 and earlier flu studies) suggest that the benefit of the mask to the wearer--excluding the benefit of the mask to others nearby from source control--is less than a 50% reduction in disease, with a 95% confidence interval centered somewhere around 20% but including zero. The RCT evidence says nothing beyond that. Public health authorities have indeed spoken with unjustified confidence as to the efficacy of masks. You're doing the same thing here in the opposite direction, though. Given the information above, can you correct your comment?
• microdrum 5y ago
  You are exactly correct, and being downvoted because of religious zealotry. This is a mathematical model. Yes, face coverings cover the face. It's a long (and ultimately disproven) leap to: face coverings materially suppress virus in a society of millions of people.
• omegaworks 5y ago
  Half the articles on your list are tangential (masks make it marginally harder to exercise, ok duh). The article posted helps us understand why the viral concentration in the environment also impacts efficacy, it helps explain why some of the articles you posted see inconclusive results.
  • toss1 5y ago
    And even the "masks make it marginally harder to exercise" is likely wrong. The winner of the 10,000m race at the 2019 USA Track & Field Championships wore a mask against his pollen allergies. [1] Worn properly, they just disappear. I wear N95s a work for many tasks, and they are mildly distracting for a few minutes, then I forget about them. Even more so now with wearing them for the pandemic. Yes, education about masks could be a LOT better, but using that is more anti-mask FUD is borderline sociopathic. [1] https://www.oregonlive.com/trackandfield/2011/06/galen_rupp_overcomes_the_polle.html https://www.oregonlive.com/trackandfield/2011/06/galen_rupp_...
    • makomk 5y ago
      According to that article, the winner of the 10,000m race wore a mask to protect against his allergies for the first 4,000m, by which point it was just too uncomfortable to continue wearing: "Rupp said Salazar told him to “wear it as long as you can. As soon as it starts to get real hot or uncomfortable, or starts to stick and get sweaty, throw it off.” The mask came flying off after 4,000 meters. But Rupp was content to bide his time until the 9,200-mark."
      • toss1 5y ago
        Right, and during that time, he was respirating at around 20X the rate of you or I sitting here. 1 MET, or Metabolic Equivalent Task, is about 3.5 mL of oxygen per kilogram per minute, which is roughly equivalent to the energy expended when sitting quietly. [1] The Vo2max of high-level athletes runs up to 97.5mL/kg [2] Sure, he used it for 'only' 40% of the race. In a national championship where fractions of a percent of O2 uptake make the difference in winning. The point is that he still wore it, running in the pack of a national championship, for nearly two and a half miles (400m=2.585mi), over 11 minutes, respirating at a level that you literally cannot imagine if you can post that comment. The mask neither slowed him enough to take him out of contention, nor did it create sufficient oxygen debt that he could not win. IOW, the mask had a completely marginal effect at levels of respiration more than an order of magnitude beyond any ordinary activity. Moreover, since air resistance increases roughly with the square of velocity, a first approximation of any mask drag or throttling he experienced vs normal respiration is not 20X, but more like 400x what a normal person would experience. And even your own citation points to it being "uncomfortable, sticky or sweaty", in the context of a national championship race, not being any kind of oxygen hinderence. And yet you want to claim that this can be ignored because he didn't wear it the whole time. So, yes, everyone knows that masks can be mildly uncomfortable, even during exercise. But they are a helluva lot less uncomfortable than enduring that respiratory/vascular disease, and a lot more ethical than spreading it. [1] https://en.wikipedia.org/wiki/Metabolic_equivalent_of_task https://en.wikipedia.org/wiki/Metabolic_equivalent_of_task [2] https://www.topendsports.com/testing/records/vo2max.htm https://www.topendsports.com/testing/records/vo2max.htm
• jmull 5y ago
  You really hurt your credibility when the first link doesn’t support the argument you claim it does.
• oasisbob 5y ago
  Here is a recent published review for those seeking a more comprehensive and complete evaluation of the literature: Howard, Jeremy, et al. "An evidence review of face masks against COVID-19." Proceedings of the National Academy of Sciences 118.4 (2021). https://www.pnas.org/content/118/4/e2014564118 https://www.pnas.org/content/118/4/e2014564118
  • irq11 5y ago
    That is a joke of a “review”, and should never have been published. Consider that it doesn’t mention the only randomized controlled trial of masks and Covid ever performed (it showed no significant protective effect), which was conducted during the period the “review” was being compiled: https://www.acpjournals.org/doi/10.7326/m20-6817 https://www.acpjournals.org/doi/10.7326/m20-6817 There’s simply no excuse. the authors cherry-pick and misinterpret top-line data to craft a narrative. It’s not a review, it’s an editorial.
    • oasisbob 5y ago
      I'm not familiar with that study, but I think it's important to note that the PNAS article was submitted mid-2020, so it's hard to understand your criticism here.
    • cr1895 5y ago
      You should note well that the study you point out made no assessment of whether mask wearing reduced the risk of spread from the mask wearer to others, which is a key point of the utility of mask-wearing during this pandemic. It is very deceptive for you to claim that this is the only trial of “masks and COVID” when you omit that nuance.
• cataflam 5y ago
  > Meanwhile, they ignore the dozens of studies showing masks are ineffective, or even counterproductive Let's try to figure out how well your summary is actually supported by your citations, especially as TFA is about medical masks and N95 masks and doesn't mention cloth masks. TL;DR: It's not (and ignores the multiple studies showing surgical and N95 masks are effective to prevent SARS-CoV infections). What your citations say is "cloth masks seem ineffective (but not surgical/N95), masks in general seem to protect less from influenza than coronaviruses, and wearing a mask may have some effect on exercise (although magnitude of the effect and consequences are unclear)". I wouldn't have had a problem with that statement. Whether that's the whole story or cherry-picking of studies is another question. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ (2015) Shows that cloth masks are less effective than medical masks... and incidentally that medical masks are effective. One study in, already contradicts your statement. https://pubmed.ncbi.nlm.nih.gov/29395560/ https://pubmed.ncbi.nlm.nih.gov/29395560/ (2017) Not about mask efficacy in disease prevention, but effects on exercise. No difference in distance, heart rate, O2 saturation, but 20% higher shortness of breath. https://pubmed.ncbi.nlm.nih.gov/32590322/ https://pubmed.ncbi.nlm.nih.gov/32590322/ (2020) Not about mask efficacy in disease prevention, but effects on exercise again. Also, not an experimental study but a comment/hypothesis. https://pubmed.ncbi.nlm.nih.gov/15340662/ https://pubmed.ncbi.nlm.nih.gov/15340662/ (2004) Not about mask efficacy in disease prevention, again. Study on patients with end-stage renal disease. https://pubmed.ncbi.nlm.nih.gov/26579222/ https://pubmed.ncbi.nlm.nih.gov/26579222/ (2015) Not about mask efficacy in disease prevention, again. Study on pregnant women. https://pubmed.ncbi.nlm.nih.gov/31159777/ https://pubmed.ncbi.nlm.nih.gov/31159777/ (2019) First interesting one. Show that viruses may deposit on the outer surface of medical masks. May prove useful in educating people to handle with care (although it seems that contamination by touching contaminated surfaces accounts for a negligible amount). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/ (2012) Ah, better. Review of a small number of other studies, focused on influenza and close contact with an infected patient. Does not conclude masks are ineffective, but more that good data and studies are hard to come by, that the studies they reviewed were between inconclusive and positive, and they may be protective when combined with other hygiene practices. Also notes that the studies on SARS coronavirus transmission found masks protective, but the results may or may not apply for influenza. It also notes compliance and correct usage are likely factors in reduced effectiveness. So, while this is the closest so far to your assertion, it doesn't quite support it either. Annex 5 in particular shows that the SARS coronavirus studies reviewed seem to show a protective effect. Much larger and wider reviews, that include this one, reach different conclusions for the topic at hand. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8084286/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8084286/ and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718106/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718106/ https://pubmed.ncbi.nlm.nih.gov/19216002/ https://pubmed.ncbi.nlm.nih.gov/19216002/ (2008) Lol. Study on 32 health-care workers, and the incidence of common cold. There was 1 cold in each group. Sample way too small to reach any conclusion, as they themselves conclude. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ Same article as the first one in the list. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2493952/pdf/annrcse01509-0009.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2493952/pdf/ann... (1981) Interesting, although a small trial study. But it only cares about a very specific thing: the efficiency of masks in surgery to avoid contaminating an open wound, unrelated to the airborne spread of respiratory diseases. More studies and reviews have followed, with mitigated results, see for example https://pubmed.ncbi.nlm.nih.gov/33039336/ https://pubmed.ncbi.nlm.nih.gov/33039336/ Interesting but irrelevant for the topic at hand. https://www.nap.edu/catalog/25776/rapid-expert-consultation-on-the-effectiveness-of-fabric-masks-for-the-covid-19-pandemic-april-8-2020 https://www.nap.edu/catalog/25776/rapid-expert-consultation-... (2020) Expert consultation, limited to the effectiveness of homemade fabric masks. It says verbatim: "It does not apply to either N95 respirators or medical masks." (and it doesn't even conclude that homemade cloth masks are ineffective, only that more research is required). https://www.nap.edu/read/25776/chapter/1#6 https://www.nap.edu/read/25776/chapter/1#6 That's the same as the article just above. Could be the 2nd honest error of course, or could be a sign you've copy/pasted part or all of the list with little editing/proofreading. https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article (2020) Review of multiple measures against influenza contamination, that seems to show no effectiveness. The authors point out themselves the limitations of the study however, small sample size and compliance issues. It's an interesting data point, but it targets influenza and I wouldn't say it disproves masks effectiveness. When looking at the bigger picture, and more and larger review, doesn't yield the same conclusions. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718106/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718106/ that includes this study among those reviewed. Interestingly, it seems to show much more conclusive results for coronavirus infection prevention than influenza, and cautions against cloth masks. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599448/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599448/ (2019) Physical study of filtering efficiency of cloth masks vs surgical masks, especially after washing https://www.acpjournals.org/doi/10.7326/M20-1342 https://www.acpjournals.org/doi/10.7326/M20-1342 (2020) One of many physical studies on patients coughing in a petri dish with various mask types. Only 4 patients, and one of the only such physical studies I've seen that didn't show a significant effect. https://link.springer.com/article/10.1007/s00392-020-01704-y https://link.springer.com/article/10.1007/s00392-020-01704-y (2020) Another one that talks about exercise and not infection. --- Looking in general at country-level data, using masks earlier seems to be significantly associated with lower mortality. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695060/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695060/ for a wide study and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7392429/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7392429/ for a small comment