The actual paper: https://www.poverty-action.org/sites/default/files/publications/Mask_RCT____Symptomatic_Seropositivity_083121.pdf https://www.poverty-action.o

The actual paper: https://www.poverty-action.org/sites/default/files/publications/Mask_RCT____Symptomatic_Seropositivity_083121.pdf https://www.poverty-action.org/sites/default/files/publicati... The study found an effect size of zero in the cloth mask cohort, and an 11% difference in the surgical mask cohort. Effect sizes that managed significance were just barely significant, at a p-value of 0.043. Also, the researchers didn't do any baseline serology, so it's quite difficult to know if there was a starting bias influencing the final results. It's also difficult to know the degree to which the non-blinded nature of the study and voluntary seroprevalence testing biased the outcome. At such small effect sizes, questions like these matter a great deal. Nevertheless, it is encouraging that someone actually bothered to do a proper RCT of masking as "protection for others", and this study has several points that should be widely communicated (e.g. the ineffectiveness of cloth masks). However, I would not say that "masks passed their test" is really one of them...these results are pretty mediocre. Vinay Prasad of UCSF has made an excellent summary of the results of the Bangladesh RCT, and I recommend it strongly: https://twitter.com/VPrasadMDMPH/status/1435679462142607361 https://twitter.com/VPrasadMDMPH/status/1435679462142607361