| > To say that cloth masks "haven't been shown to help do anything" is demonstrably false From the only RCT I'm aware of having been published during the pandemic[1]: > the difference observed was not statistically significant The full quote is: > Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection. But the important part is the difference observed was not statistically significant, not just because statistically significance is counted as significant for good reason, but because there's a possible 23% greater chance of infection. That's quite the swing, and something that's been seen before[2]: > Conclusions This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated. That's without going into the many statements by leading doctors of the public health response during the pandemic (like Fauci or Jenny Harries). This helpful Spectator article[3] goes over the damning lack of evidence there's been since long before this pandemic and also lists a few to watch out for. Still not heard any demonstrable falsification coming from an rct yet though. I wonder how long we'll have to wait? Of course, we could always rely on reviews instead of randomised controlled trials, they give much better results… <cough> <cough> Excuse me while I put on my mask. Note: this response was made in good faith ;-) [1] https://www.acpjournals.org/doi/10.7326/M20-6817 [2] https://bmjopen.bmj.com/content/5/4/e006577 [3] https://www.spectator.co.uk/article/how-much-do-face-masks-a... |
However, the correct answer to a non-significant study is not to assume that there is no difference, rather that we have not been able to detect a difference.
The results section:
A total of 3030 participants were randomly assigned to the recommendation to wear masks, and 2994 were assigned to control; 4862 completed the study. Infection with SARS-CoV-2 occurred in 42 participants recommended masks (1.8%) and 53 control participants (2.1%). The between-group difference was −0.3 percentage point (95% CI, −1.2 to 0.4 percentage point; P = 0.38) (odds ratio, 0.82 [CI, 0.54 to 1.23]; P = 0.33). Multiple imputation accounting for loss to follow-up yielded similar results. Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection.
So, overall there were 95 participants who got a Covid diagnosis, of the 6k enrolled, and the 4.8k who completed the study.
This is basically noise. My personal prior is that had this study taken place in the US or Brazil, we would have been able to detect an effect. However, clearly I don't have any evidence for this.
tl;dr that study gives us very little information, because the baseline prevalance of Covid was so low that we don't have enough power to detect a difference between the two groups. This is consistent with a finding of masks don't work, and masks work (but we can't detect the difference in this study).