Mask wearing for COVID is targeted at reducing likelihood of spreading to someone else.
> If you try to break the analysis down according to specific lines of evidence (i.e. source control for the public), you quickly find that there's not enough data to draw any conclusion.
We're going to get a lot of data soon, but for the time being, it's probably best to err on the side of "something that stops droplets probably helps stop a disease spread by droplets".
> Our search identified 172 observational studies across 16 countries and six continents, with no randomised controlled trials and 44 relevant comparative studies in health-care and non-health-care settings (n=25 697 patients). Transmission of viruses was lower with physical distancing of 1 m or more, compared with a distance of less than 1 m (n=10 736, pooled adjusted odds ratio [aOR] 0·18, 95% CI 0·09 to 0·38; risk difference [RD] −10·2%, 95% CI −11·5 to −7·5; moderate certainty); protection was increased as distance was lengthened (change in relative risk [RR] 2·02 per m; pinteraction=0·041; moderate certainty). 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). Eye protection also was associated with less infection (n=3713; aOR 0·22, 95% CI 0·12 to 0·39, RD −10·6%, 95% CI −12·5 to −7·7; low certainty). Unadjusted studies and subgroup and sensitivity analyses showed similar findings.
The important bit here (for everyone saying we have great evidence that masks work) is that "low certainty" bit. That's GRADE, and it means "low certainty (our confidence in the effect estimate is limited; the true effect could be substantially different from the estimate of the effect);" So, maybe masks are substantially less, or more, protective.
Last time it was pointed out "low certainty" doesn't mean what you imply it does (https://news.ycombinator.com/item?id=23434344) you let it sail on by.
Just so we're clear: you've never linked to research to support any of your points, because you're not able to, are you?
I did. 28 days ago.
https://news.ycombinator.com/item?id=23434255
https://news.ycombinator.com/item?id=23434053
> Here's what low certainty grade results mean: "low certainty (our confidence in the effect estimate is limited; the true effect could be substantially different from the estimate of the effect);".
You're acting like its definition is "it's probably the opposite, and thus is evidence for my argument".
Here's someone explaining what GRADE means:
https://twitter.com/dnunan79/status/1269014574478626819
"I teach GRADE
If something has “low quality” evidence, it means the observed estimate is highly likely to be different from the truth.
Face masks = low quality evidence.
So what’s the point of GRADE if we can conclude “evidence shows”?"
EDIT: Your link even says this
> 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
If you read the Lancet paper, you'll find that they pooled papers for source control and PPE together to arrive at their conclusions. In fact, most of the papers they used in that meta-analysis were for surgical masks used as PPE (personal protective equipment) in a medical setting.
In other words, the advocates for masking are doing the same thing that you're saying is weird. If you try to break the analysis down according to specific lines of evidence (i.e. source control for the public), you quickly find that there's not enough data to draw any conclusion.
On the other hand, the argument in favor of this kind of pooling is straightforward: if your end goal is to reduce transmission of a virus, and you find that goggles are highly effective at preventing infection, then it doesn't matter very much. Tell everyone to wear goggles instead, and forget about the masks. Transmission will still be reduced.