Regarding Danish study, here's what I found: the authors concluded that “the 95% confidence intervals are compatible with a possible 46% reduction to 23% increase in infections among mask wearers. These findings do offer evidence about the degree of protection mask wearers can anticipate in a setting where others are not wearing masks and where other public health measures, including social distancing, are in effect. The findings, however, should not be used to conclude that a recommendations for everyone to wear masks in the community would not be effective in reducing SARS-CoV-2 infections, because the trial did not test the role of masks in source control of SARS-CoV-2 infection.”

Although this was a well-designed study, it had several key limitations. During the study period, there was a low burden of community COVID-19 infections in Denmark, and the study intervention only lasted for 1 month. Cafés and restaurants were closed for the first half of the study. Mask adherence relied on retrospective self-reports. Participants in the mask group had more documented household COVID-19 infections (n= 52) than in the control group (n=39). The antibody test used for diagnosis of COVID-19 infection had a sensitivity of only 82.5%. Finally, there was a trend toward protection in the mask group, which could have been significant had more subjects been recruited to the study or if the community burden of COVID-19 had been higher.

Please consider following two writings:

[1]: https://www.medrxiv.org/content/10.1101/2020.07.31.20166116v...

[2]: https://wmjonline.org/wp-content/uploads/2020/119/4/229.pdf