COVID-19 Resource Center

COVID-19 Resource Center

Disclosures: Bhatt reports he has financial ties with numerous pharmaceutical and device companies. The other study authors and the editorial authors report no relevant financial disclosures.
July 15, 2020
2 min read

Universal masking lowers SARS-CoV-2 infection in health care workers

Disclosures: Bhatt reports he has financial ties with numerous pharmaceutical and device companies. The other study authors and the editorial authors report no relevant financial disclosures.
You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

In a 12-hospital health care system, universal masking was associated with lower rates of testing positive for SARS-CoV-2 in health care workers, according to a research letter published in JAMA.

Deepak L. Bhatt

“Perhaps some people were unwilling to wear a mask during this COVID-19 pandemic due to lack of data. Well, now we have strong data from Mass General Brigham that support masking. While our study was in health care workers, the results should apply in other situations where social distancing is not possible. So, at this point, there is no longer any excuse not to wear a mask,” Cardiology Today Intervention Section Editor Deepak L. Bhatt, MD, MPH, executive director of interventional cardiovascular programs at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School, told Healio.

Source: Adobe Stock.

Bhatt and colleagues analyzed 9,850 health care workers from the Mass General Brigham health care system tested for SARS-CoV-2 with reverse transcriptase-polymerase chain reaction in March and April. The main criterion for testing was having symptoms consistent with SARS-CoV-2 infection. Universal masking for workers at the hospitals began March 25.

Participants were stratified into three categories: those tested before the health care system implemented universal masking (March 1-24), those tested during a transition period and a lag period to allow manifestations of symptoms (March 25-April 10) and those tested during the implementation period (April 11-30).

Among the cohort, 12.9% tested positive for SARS-CoV-2 (median age, 39 years; 73% women; 7.4% physicians or trainees; 26.5% nurses or physician assistants; 17.8% technologists or nursing support; 48.3% other job categories), according to the researchers.

In the preintervention period, the rate of positive tests increased from 0% to 21.32% (weighted mean increase, 1.16% per day; case doubling time, 3.6 days; 95% CI, 3-4.5), whereas in the intervention period, the rate of positive tests declined from 14.65% to 11.46% (weighted mean decrease, 0.49% per day; net slope change, 1.65%; 95% CI, 1.13-2.15; P < .001), Bhatt and colleagues wrote.

“The case number continued to increase in Massachusetts throughout the study period, suggesting that the decrease in the SARS-CoV-2 positivity rate in Mass General Brigham health care workers took place before the decrease in the general public,” Bhatt and colleagues wrote. “Randomized trials of universal masking of health care workers during a pandemic are likely not feasible. Nonetheless, these results support universal masking as part of a multipronged infection reduction strategy in health care settings.”

In a related editorial, John T. Brooks, MD, a medical epidemiologist with the Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention at the CDC, and colleagues wrote: “Data from a large health care system may be generalizable to the greater community insofar as the findings represent the contribution of masking when individuals are physically close to one another and social distancing is not possible.


“The public needs consistent, clear and appealing messaging that normalizes community masking,” they wrote. “At this critical juncture when COVID-19 is resurging, 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.”

Bhatt noted that there are still many important research questions, “though these open issues shouldn’t detract from the main message to the public, which is to wear a mask — any type is better than none.”

However, he said, “medicine and science always benefit from more investigation and we need to identify optimal mask designs that provide appropriate degrees of protection in a user-friendly, comfortable, cost-effective manner, both for health care workers and the lay public.”

For the latest news on COVID-19 including case counts, information about the global public health response and emerging research, please visit the COVID-19 Resource Center on Healio.


Editor's note: This article was updated on July 16, 2020, with quotes from an interview with Deepak L. Bhatt, MD, MPH.