Face masks give no additional COVID defense to social distancing: Danish study

Mask wearers are no better defended against COVID-19 than their mask-shunning counterparts, according to a Danish study of almost 5,000 people, roughly half of whom wore face masks as COVID-19 protection in April and May.

The infection rate was 1.8% among the masked (42 of 2,392) and 2.1% among the unmasked (53 of 2,470).

The participants were volunteer adults who regularly spent at least three hours a day outside their homes in a community with some social distancing and moderate infection levels.

Annals of Internal Medicine published the study online Nov. 18.

Lead author Henning Bundgaard, DMSc, of Copenhagen University and colleagues acknowledge as a limitation their omission of data on the important flipside of the equation: face masks’ ability to protect the community from infected mask wearers.

During the study period, masks were officially recommended in Denmark but only spottily used.

“The recommendation to wear surgical masks to supplement other public health measures did not reduce the SARS-CoV-2 infection rate among wearers by more than 50% in a community with modest infection rates, some degree of social distancing, and uncommon general mask use,” Bundgaard et al. comment in their discussion section.

The study’s findings suggest, however, that people “should not abandon other COVID-19 safety measures regardless of the use of masks.

“While we await additional data to inform mask recommendations, communities must balance the seriousness of COVID-19, uncertainty about the degree of source control and protective effect, and the absence of data suggesting serious adverse effects of masks.”

The study is available in full for free.