People should wear masks. Masks may help prevent the spread of covid-19.
This study talks about N95 or 12 to 16 layer cotton masks. Most members of the public are using much less. It rates the quality of evidence for masks as "low certainty", which means masks might be very much less effective (or very much more effective) than they estimate.
Face mask use could result in a large reduction in risk of infection (n=2647; aOR 0·15, 95% CI 0·07 to 0·34, RD −14·3%, −15·9 to −10·7; low certainty), with stronger associations with N95 or similar respirators compared with disposable surgical masks or similar (eg, reusable 12–16-layer cotton masks; pinteraction=0·090; posterior probability >95%, low certainty)
Further high-quality research, including randomised trials of the optimum physical distance and the effectiveness of different types of masks in the general population and for health-care workers' protection, is urgently needed.
Although direct evidence is limited, the optimum use of face masks, in particular N95 or similar respirators in health-care settings and 12–16-layer cotton or surgical masks in the community, could depend on contextual factors; action is needed at all levels to address the paucity of better evidence. Eye protection might provide additional benefits. Globally collaborative and well conducted studies, including randomised trials, of different personal protective strategies are needed regardless of the challenges, but this systematic appraisal of currently best available evidence could be considered to inform interim guidance.
Given the low prevalence of COVID-19 currently, even if facemasks are assumed to be effective, the difference in infection rates between using facemasks and not using facemasks would be small.Assuming that 20% of people infectious with SARS-CoV-2 do not have symptoms,and assuming a risk reduction of 40% for wearing facemask, 200000 people would need to wear facemasks to prevent one new infection per week in the current epidemiological situation.
One of the problems of DIY cloth masks being recommended to the public is that they start to lose effectiveness as soon as you put them on. https://www.ijic.info/article/view/10788
One of the problems of DIY cloth masks being recommended to the public is that they start to lose effectiveness as soon as you put them on. https://www.ijic.info/article/view/10788
Your summary doesn’t match that of the linked study, which says:
Face masks significantly decreased bacterial dispersal initially but became almost ineffective after two hours of use.
Also the study takes its measurement at 10-12cm away. I would be interested in other distances, bc idk about you but I’m never usually that close to someone’s face in public.
Viral load in the area tested (a theatre in this instance), both with and without masks, would have been something of interest too.
If we could also have real-world data comparing infection rates between two control groups, even better.
There’s also stuff like this[0]:
If two people are wearing masks, the viral particles can travel about 5 feet away from each individual. When an infected person is not wearing a mask, those particles can float through the air 30 feet or more and stay alive for up to 30 hours.
I do appreciate you taking the time to respond and provide sources for your claim.
However, I find that your linked resources are not compelling and do not support your original statement. The Norwegian article is particularly light on details/data - which I can forgive seeing as it’s literally labelled a “memo” and a also a “rapid review”
Comments
What is the weak evidence for mask wearing?
People should wear masks. Masks may help prevent the spread of covid-19.
This study talks about N95 or 12 to 16 layer cotton masks. Most members of the public are using much less. It rates the quality of evidence for masks as "low certainty", which means masks might be very much less effective (or very much more effective) than they estimate.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
Norway have some interesting modelling: https://www.fhi.no/globalassets/dokumenterfiler/rapporter/20...
One of the problems of DIY cloth masks being recommended to the public is that they start to lose effectiveness as soon as you put them on. https://www.ijic.info/article/view/10788
Your summary doesn’t match that of the linked study, which says:
Also the study takes its measurement at 10-12cm away. I would be interested in other distances, bc idk about you but I’m never usually that close to someone’s face in public.
Viral load in the area tested (a theatre in this instance), both with and without masks, would have been something of interest too.
If we could also have real-world data comparing infection rates between two control groups, even better.
There’s also stuff like this[0]:
I do appreciate you taking the time to respond and provide sources for your claim.
However, I find that your linked resources are not compelling and do not support your original statement. The Norwegian article is particularly light on details/data - which I can forgive seeing as it’s literally labelled a “memo” and a also a “rapid review”
[0] https://med.stanford.edu/news/all-news/2020/06/stanford-scie...
If you're going to ignore a major study published by The fucking Lancet there's nothing I could say that would persuade you, is there?