Researchers at Mass General Brigham, one of Harvard’s teaching hospital groups, found that in early 2020, before mask mandates were introduced, the infection rate among health care workers doubled every 3.6 days and rose to 21.3 percent. After universal masking was required, the rate stopped increasing, and then quickly declined to 11.4 percent.
In Germany, 401 regions introduced mask mandates at various times over three months in the spring of 2020. By carefully comparing otherwise similar places before and after mask mandates, researchers concluded that “face masks reduce the daily growth rate of reported infections by around 47 percent,” with the effect more pronounced in large cities and among older people.
Brown, who led the Cochrane review’s approval process, told me that mask mandates may not be tenable now, but he has a starkly different feeling about their effects in the first year of a pandemic.
“Mask mandates, social distancing, the other shutdowns we had in terms of even restaurants and things like that — if places like New York City didn’t do that, the number of deaths would have been much higher,” he told me. “I’m very confident of that statement.”