Lots of immediate reaction denigrating the Danish mask study, even from some of it’s researchers....but it’s pretty devastating. And it’s a fully randomized trial, unlike so many of the others. Oops there goes Biden’s main solution to Covid:
6000 people participated in the study. 3030 were randomly assigned to the mask group and 2994 to the control arm. Out of the entire group 4862 completed the study period. These were adults who spent more than 3 hours a day outside their homes and didn’t wear masks at an occupation. Both the mask wearing arm and the non-mask wearing arm were told to follow social distancing measures. The mask-wearing group was encouraged to wear a mask outside their home and were given 50 surgical masks for this purpose. So better masks than cloth ones. The primary outcome was number of infections after one-month. 42 people got infected in the mask wearing group and 53 in the control group. Because more dropouts occurred in the mask group, there was no statistical difference in infection rate. One interesting little nugget in the characteristics of the groups is that more people in the control arm had what might be considered higher-risk occupations than in the mask wearing arm. Yet still no difference in infection rate.
Some of the criticisms are that the data on mask usage were self-reported, this only tested the effect on the mask wearer, not whether they might be less likely to infect others, and other niggling concerns. The real criticism is that it doesn’t fall in line with the orthodoxy on all of us needing a mask glued to our face 24 by 7. Self-reported adherence was good, with over 90% of the mask-wearers saying they largely complied with the recommendation and almost half saying they always did. Taking out the 7% who reported poor adherence did not change the primary finding. And very importantly, looking only at those persons who reported always complying with the mask recommendation also did not change the outcome. It appeared there was very low in-home transmission that caused the infection in either arm of the study, so most transmission was occurring in the community. Another interesting finding was no difference in infection with other respiratory viruses.
This was a well-designed study. If masks made a difference in the community, it would have been seen in this large a group. And that distinction between protecting the wearer versus others makes no logical sense. Think about it. If wearing a mask doesn’t do a better job of keeping you from getting infected, i.e. keeping the virus from coming in, why would it do a better job of keeping it from going out? In fact, you might expect the opposite, there is less pressure in the inhale than the exhale.