Researchers in Denmark reported on Wednesday that surgical masks did not protect the wearers against infection with the coronavirus in a large randomized clinical trial. But the findings conflict with those from a number of other studies, experts said, and is not likely to alter public health recommendations in the United States.
The study, published in the Annals of Internal Medicine, did not contradict growing evidence that masks can prevent transmission of the virus from wearer to others. But the conclusion is at odds with the view that masks also protect the wearers — a position endorsed just last week by the Centers for Disease Control and Prevention.
Critics were quick to note the study’s limitations, among them that the design depended heavily on participants reporting their own test results and behavior, at a time when both mask-wearing and infection were rare in Denmark.
Coronavirus infections are soaring throughout the United States, and even officials who had resisted mask mandates are reversing course. Roughly 40 states have implemented mask requirements of some sort, according to a database maintained by The New York Times.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, advocates a national mask mandate, as does President-elect Joe Biden.
“I won’t be president until January 20th, but my message today to everyone is this: wear a mask,” Biden recently wrote on Twitter.
From early April to early June, researchers at the University of Copenhagen recruited 6,024 participants who had been tested beforehand to be sure they were not infected with the coronavirus.