How does the virus spread? Mostly by riding on tiny water droplets coming out of your mouth and nose, which the mask catches by absorption
This is a model that may makes sense but in the end it leads to the wrong conclusions, as proved by the systematic review by Cochrane.
Perfect is the enemy of good.
Read the review: the effectiveness of masks is close to zero, not 90%, nor 50% and nor 10% as you seem to imply.
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@freemo @post @feld yes that's a very non-conclusive systematic review. The authors conclude that the variability in the studies and the low adherence with the masking interventions means they can't say with any confidence whether the effect size estimate is at all accurate. That's a great paper to cite to show we don't actually know if masks work!
You are clearly not used to this kind of papers, it is normal to use cautious sentences to this extent and you should focus on the results instead:
“We included 12 trials (10 cluster‐RCTs) comparing medical/surgical masks versus no masks to prevent the spread of viral respiratory illness (two trials with healthcare workers and 10 in the community). Wearing masks in the community probably makes little or no difference to the outcome of influenza‐like illness (ILI)/COVID‐19 like illness compared to not wearing masks (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.84 to 1.09; 9 trials, 276,917 participants; moderate‐certainty evidence. Wearing masks in the community probably makes little or no difference to the outcome of laboratory‐confirmed influenza/SARS‐CoV‐2 compared to not wearing masks (RR 1.01, 95% CI 0.72 to 1.42; 6 trials, 13,919 participants; moderate‐certainty evidence). Harms were rarely measured and poorly reported (very low‐certainty evidence).
We pooled trials comparing N95/P2 respirators with medical/surgical masks (four in healthcare settings and one in a household setting). We are very uncertain on the effects of N95/P2 respirators compared with medical/surgical masks on the outcome of clinical respiratory illness (RR 0.70, 95% CI 0.45 to 1.10; 3 trials, 7779 participants; very low‐certainty evidence). N95/P2 respirators compared with medical/surgical masks may be effective for ILI (RR 0.82, 95% CI 0.66 to 1.03; 5 trials, 8407 participants; low‐certainty evidence). Evidence is limited by imprecision and heterogeneity for these subjective outcomes. The use of a N95/P2 respirators compared to medical/surgical masks probably makes little or no difference for the objective and more precise outcome of laboratory‐confirmed influenza infection (RR 1.10, 95% CI 0.90 to 1.34; 5 trials, 8407 participants; moderate‐certainty evidence). Restricting pooling to healthcare workers made no difference to the overall findings. Harms were poorly measured and reported, but discomfort wearing medical/surgical masks or N95/P2 respirators was mentioned in several studies (very low‐certainty evidence).
One previously reported ongoing RCT has now been published and observed that medical/surgical masks were non‐inferior to N95 respirators in a large study of 1009 healthcare workers in four countries providing direct care to COVID‐19 patients.”
Oh and also just look at the parts that you highlighted and ignore the parts you dont highlight where it says things like “low‐certainty evidence”.
The point was indeed stressing the conclusions and show how your “it says there is not enough evidence” doesn’t reflet at all the abstract. The one cherry-picking was you and it is clear since if you had to highlight those parts they would be way less than my highlights.
@post
thats some impressive cherry picking… So we shoudl ignore the author of this highly superior study completely when they tell us the poor quality of studies, and instread should trust you that the studies are in fact very well done and complete… but only the studies that aghree with you of course, not all those other studies that disagree.
Oh and also just look at the parts that you highlighted and ignore the parts you dont highlight where it says things like “low‐certainty evidence”.
@chiasm @feld