Danish study finds face masks provide limited protection to wearer

A Danish study released on Wednesday found face masks provide the wearer with only limited protection against Covid-19 infection, but said this should not be used to argue against their widespread use to prevent people infecting others.

In the study, which was carried out in April and May when Danish authorities did not recommend wearing face masks, 6,024 adults were divided into two groups, one wearing face masks and one control group.

After one month, 1.8% of the people wearing masks had been infected, while 2.1% of the people in the control group had tested positive, Copenhagen University Hospital said in a press release.

“The study does not confirm the expected halving of the risk of infection for people wearing face masks,” it said. “The results could indicate a more moderate degree of protection of 15-20%, however, the study could not rule out that face masks do not provide any protection.”

The findings are consistent with previous research. Health experts have long said a mask provides only limited protection for the person wearing it, but can dramatically reduce the risk to others if the wearer is infected, even when showing no symptoms. Preventing the spread to others is known as source control.

The study’s findings “should not be used to conclude that a recommendation 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,” the authors wrote.