Masks Work: Study Shows HCWs Protected Against COVID-19

July 24th, 2020

By Gary Evans, Medical Writer

A hospital study on the efficacy of mask use by healthcare workers and patients in preventing novel coronavirus transmission is being cited by public health officials in support of recommendations for universal masking in the community.

“While we studied health care workers, the results also apply to other situations in which social distancing is not possible,” says lead author Deepak Bhatt, MD, MPH, of Brigham and Women’s Hospital, Boston, MA. “For those who have been waiting for data before adopting the practice, this paper makes it clear: Masks work.”

The study was conducted at 12 hospitals in the Mass General Brigham (MGB) system. In March 2020, MGB began SARS-CoV-2 testing of symptomatic healthcare workers and universal masking of all staff and patients. Surgical masks were provided to patients by the hospitals.

Overall, 9,850 healthcare workers were tested and 1,271 (12.9%) were positive for SARS-CoV-2. These included 7.4% physicians or trainees, 26.5% nurses or physician assistants, 17.8% technologists or nursing support, and 48.3% other.

“During the preintervention period, the SARS-CoV-2 positivity rate increased exponentially from 0% to 21.3%, with a weighted mean increase of 1.1% per day and a case doubling time of 3.6 days,” the authors found. “During the intervention period, the positivity rate decreased linearly from 14.6% to 11.4%, with a weighted mean decline of 0.49% per day. Universal masking at MGB was associated with a significantly lower rate of SARS-CoV-2 positivity among healthcare workers.”

Although the results could be confounded by other variables to some degree, the number of COVID-19 cases continued to increase in Massachusetts over the study period. That suggests the reduction in COVID-19 in healthcare workers occurred before the decrease in the community, the authors noted.

Hospital staff wore surgical masks in general, and N95 respirators masks when caring for known or suspected COVID-19 patients, Bhatt says.

“We did not assess compliance in our study, though what I saw on the wards was 100% compliance,” he adds. The results can “absolutely” be extrapolated to other hospitals who adopt universal masking of staff and patients, he says.

For more on this story, see the September 2020 issue of Hospital Employee Health.