Universal masking of all health care workers and patients at Mass General Brigham (MGB), the largest health care system in Massachusetts, was associated with significantly lower rates of health care workers testing positive for COVID-19. The study, published in the Journal of the American Medical Association, suggests the association "may be related to a decrease in transmission between patients and health care workers and among health care workers."

Xiaowen Wang, MD, et al., identified 9,850 health care workers at MGB who were tested for COVID-19 between March 1 and April 30, 2020. The primary criterion for testing was having symptoms consistent with the virus. The median age of those tested was 39 years and 73% were female; 7.4% were physicians or trainees and 26.5% were nurses or physician assistants. Of those tested, 1,271 (12%) had positive results.

Wang and colleagues noted that prior to implementing universal masking (the pre-intervention period), the COVID-19 positivity rate among health care workers "increased exponentially" from 0 to 21.32%. However, this rate declined significantly – from 14.65% to 11.46% – once masking was required for both patients and health care workers.

While the decrease in health care worker infections could be confounded by other state-wide measures both inside and outside the health system, the authors highlight that COVID-19 cases were on the rise in Massachusetts throughout the study period, suggesting the decrease in positive testing within MGB took place before the decrease in the general public.

"Based on this research, masks work in public," says Deepak L. Bhatt, MD, MPH, FACC, one of the study's authors. "Hopefully, these data can help convince those who are still in doubt and thereby save many lives globally. The very insightful editorial from the Centers for Disease Control and Prevention (CDC) leadership got it right – the time for universal masking is now!"

In the CDC editorial, John T. Brooks, MD; Jay C. Butler, MD; and Robert R. Redfield, MD, write that "with cloth face coverings, personal protection is derived from their use by all members of the community." They note that "public health officials and leaders need to ensure that the public understands clearly when and how to wear cloth face coverings properly and continue building the evidence base for their effectiveness." They also acknowledge the need for innovation to extend the physical comfort and use of masks. "At this critical juncture when COVID-19 is resurging," they write, "broad adoption of cloth face coverings is a civic duty, a small sacrifice reliant on a highly effective low-tech solution that can help turn the tide favorably in national and global efforts against COVID-19."

Clinical Topics: Cardiovascular Care Team, COVID-19 Hub

Keywords: Leadership, Public Health, COVID-19, severe acute respiratory syndrome coronavirus 2, Health Personnel, Centers for Disease Control and Prevention, U.S., Physician Assistants, Physicians

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