The State of Denmark

A Danish study of the effects of wearing masks on contracting COVID-19, published in the Annals of Internal Medicine will probably have varying interpretations:

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.

depending on your political views. My interpretation is that although wearing masks is not useless its utility is quite limited and very possibly offset by changes in behavior on the part of people wearing masks. Or, as I have been contending for months, they’re being oversold.

I think that the present administration has been remiss in not showing a good example but rather pooh-poohing mask use but pleas for national mandates are misplaced as well. Possibly the greatest utility of masks is to convince people they’re doing something personally to contribute to the “war effort”. Combined with an organized public relations campaign, aimed less at shaming people than at encouraging them, more wearing of masks might help a little and, again combined with a public relations campaign, it isn’t particularly harmful.

To me the bottom line is that it is unlikely that the present resurgence in cases of COVID-19 can be attributed to insufficient mask-wearing or opening restaurants.

2 comments… add one
  • Drew Link

    I’m not so sure I’d attribute things to political views. I’ve made mental notes of every mask study I’ve come across. The science is very mixed. More importantly, it is clear that mask type and proper use dwarf theoretical effects. The world is not a lab environment.

    Its like the lockdowns. They work, by definition, if the world becomes a bunch of bubble boys. Its just that you can’t do it in any real world; at best you can do it to a degree that keeps the IC units less than capacity. And as we have seen, the costs outweigh the benefits, destroying livelihoods and civil liberties, while boneheaded and avoidable actions endanger the vulnerable .

  • steve Link

    I have no idea how many mask studies I have read going back over the years, but they arent really that mixed. It is clear that they work but not at a 100% level. If people dont use them, they dont work. If compliance is poor, they dont work, but then that is true of nearly every medical intervention. Also, they have very little cost. They dont close down the economy. You wear masks and distance so that the economy can continue.

    I hope the problems with this study are obvious. (Size) If you increased the numbers by 2 orders of magnitude the results likely become significant. As noted, you would find that masks provide a 23%-46% reduction in Covid. Alas, stats dont really work that way. The other issue here is that what we really want to know, at least I do, is what happens if both people wear a mask vs both people dont. Harder to study of course.


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