New research backs benefits of wearing masks to cut risk

Four months of discord about the coronavirus epidemic have transformed the cloth mask into a potent political symbol, touted by Democrats as a key part of communal responsibility, labeled by some GOP leaders as a sign of government overreach and as a scarlet letter pinned on the weak.

But as partisan interests sew symbolism and controversy into masks, scientists are trying to provide answers about how effectively those masks prevent transmission of the coronavirus, and what role they should play in efforts to limit the pathogen’s spread.

Several new studies published this month support wearing masks to curb the transmission of the novel coronavirus. The broadest, a review funded by the World Health Organization and published in the journal Lancet, concluded that data from 172 observational studies indicate wearing face masks reduces the risk of coronavirus infection.

“Our findings suggest, in multiple ways, that the use of masks is highly protective in health-care and community settings,” said the author of the review, Holger Schünemann, an epidemiologist and physician at McMaster University in Ontario.

But that conclusion came with an important caveat: “We have low certainty in that,” Schünemann said, meaning the authors cannot be strongly confident in the result. He spoke Friday from a small island in Italy where he and his wife, a fellow epidemiologist, were studying the prevalence of coronavirus antibodies.

The gold standard in science — a randomized, double-blinded controlled trial — is impossible to conduct in a pandemic, so researchers have turned to other analyses, said Andrew Noymer, an associate professor of disease prevention at the University of California at Irvine who was not part of the review.