After Brigham and Women's Hospital in Boston began requiring that nearly everyone in the hospital wear masks, new coronavirus infections diagnosed in its staffers dropped by half — or more.

Brigham and Women’s epidemiologist Dr. Michael Klompas said the hospital mandated masks for all health care staffers on March 25, and extended the requirement to patients as well on April 6.

"When we first began our universal masking policy, we had 12 to 14 new infections per day among our health care workers," he said. "And then after we instituted employee masking, that number dropped down to around eight."