Randomized controlled trials. The gold standard of science. They tell us what we need to know about statistical significance. None support masking. Three clearly do not. One suggests cloth masks are likely WORSE than nothing.
Follow the highest quality data.
Mark
It's extremely difficult do a well-designed double-blind study of the effects of masking and few have been done. I don't know how you come to the conclusion that none of such studies supports masking. Citations?
The study that has received the most attention was a Danish study published in November that anti-maskers elevated to the final word with misrepresentations of the findings as showing that masks are ineffective for COVID-19. However, even the authors of the study say the results shouldn't be interpreted to mean that masks shouldn't be worn. This was the first randomized controlled trial to report results, so I don't understand your comment that a majority of such studies had this finding.
This Danish study tested 6000 people, half of which were given 50 surgical masks and told to wear them when outside. The other half weren't given masks or that recommendation. The Danish trial was done in April and May at a time when the rate of virus circulating in Denmark was low, making it more difficult to find a protective effect. And, 47% of the people given the mask reported that they used the masks "predominantly as recommended" with 7% saying they did not used it as recommended.
The Danish study was designed to detect a large effect - 50% or more. To achieve statistical significance of finding less than 50% would have required a much larger study. Also, the study was not designed to find whether masks can prevent the spread of the virus to others - known as Source Control - thought to be the primary way masks work.
The study was done when Demark wasn't recommending this to the public, so most people they encountered were unlikely to be masked - the Source. Those in the masked group had an 18% reduction of infections which wasn't statistically significant because of the small design of the study. The authors say the findings were inconclusive. They did say that their "...findings cannot be used to recommend that masks would be ineffective, especially since it did NOT test the role of masks in Source Control."
So, it isn't known how compliant they were or whether the masks were even worn correctly. I'm sure you've noticed that many people in the U.S. don't seem to be aware that they also breathe through their noses. Compliance with the recommendations were ascertained by self-report with 54% reporting of those given masks not fully following the recommendations. We also don't know whether people wearing masks take more risk - eg do less social distancing.
It's important to distinguish between an absence of evidence and evidence of absence.
Nobody has ever claimed that masks are 100% protective. It's one of a number of safety measures. Any measure of effectiveness is important for a life-threatening disease. The overwhelming evidence suggests that masks are effective but an incorrect interpretation of this study has gone viral to justify not wearing masks. The takeaway - don't just read headlines.
For those interested in derivative findings pointing to the value of masks, check out this Comparison of Associations of State Reopenings with COVID-19 Burden. Scroll down to the graphs, the discussion, and the conclusions. https://link.springe...606-020-06277-0
While I'm posting, I'd like to mention one of my pet peeves: A year after this pandemic hit us, we STILL haven't been able to manage to produce an adequate supply of equivalent N-95 masks for the population! Other nations have done it. Many masks don't fit properly and/or have very low protective effect, including counterfeit KN-95 masks from China. Is this beyond our capabilities? Shameful.
(note to Mark: BTW, I can't seem to edit what I've written. I wanted to correct a couple of typos on one comment and also to apologize for a personal frontal attack to Rogerdoger. I thought you locked down this discussion and that was the reason for the absence of the "edit" link. Maybe it's just my computer or my very limited technical know-how.) EDIT: The link just appeared again and worked!
Edited by claire, 18 January 2021 - 01:18 PM.
