Danish mask study has serious flaws, experts say - The Washington Post

... In letters and blog posts, public health experts express concern about the design of the study and warn that policymakers could misinterpret the research to mean that masks are ineffective.
"However, the more accurate translation is that this study is uninformative regarding the benefits (or lack thereof) of wearing masks outside of the healthcare setting," one letter states.

"As such, we caution decision-makers and the media from interpreting the results of this trial as being anything other than artifacts of weak design."
https://www.washingtonpost.com/health/2020/11/20/mask-danish-study/