Medical masks as good as respirators at preventing Flu transmission

A new study coauthored by EPI researcher Derek Cummings, published today in the Journal of the American Medical Association, resolves a long running debate over whether paper medical masks or respirator-style masks are more protective for health care workers against flu.

Just in time for flu season, new research addresses a long-running controversy over whether common paper medical masks are as effective as costlier respirator-type masks in protecting health care workers from influenza and other respiratory viruses.

A study published today in the Journal of the American Medical Association compared paper medical masks, which costs about a dime, to a less commonly used respirator called an N95, which costs around one dollar. The study is the largest clinical trial of its kind and it found no significant difference in the effectiveness of the two mask types for preventing transmission of influenza or other viral respiratory illness within real-world health care settings.

“We showed there is no difference in the incidence of influenza and other common respiratory viruses among health care personnel wearing the two types of protection,” said Derek Cummings, Ph.D., professor of biology at the University of Florida’s Emerging Pathogens Institute and the College of Liberal Arts and Sciences. Cummings led the data analysis and was a co-principal investigator on the study. “This is important from a public policy standpoint because it informs guidance for protecting health care personnel from infection each season and during pandemics if one were to occur.”

Portrait of an African American female medical professional with surgical mask

When medical personnel — such as nurses, doctors, and others with direct patient contact — treat patients with contagious diseases such as flu, they risk catching the illness and must take precautions to control their own chance of infection. For example, during the 2009 outbreak of swine flu, H1N1, a large study later found that 30 percent of health care workers in emergency departments contracted the disease.

During that pandemic, the U.S. Centers for Disease Control and Prevention recommended using the N95 respirators, which are designed to fit closely over the nose and mouth and filter at least 95 percent of airborne particles, rather than the looser-fitting surgical masks routinely worn by health care workers. But some facilities had trouble replenishing N95s as supplies were used.

But even when supplies are plentiful, health care workers may be less vigilant about wearing the N95 respirators since many perceive them to be less comfortable than medical masks. It can be comparatively harder to breathe, and feel warmer on the wearer’s face, when using an N95.

While the N95 respirator mask has been shown to be far more effective at filtering viral particles in simulated laboratory studies, these studies did not account for the pragmatic and logistical decisions health care personnel make in the field. For example, many users may leave the mask hanging around their neck in between patients. The few studies that have compared the masks and respirators in active health care settings used much smaller numbers of individuals and yielded mixed results. This lack of clarity has led to a running debate about which mask works best, resulting in a mixed bag of positions and practices held by varying clinical, public health and regulatory organizations. 

The new study was performed at multiple medical settings in seven cities around the country, including Houston, Denver, Washington, D.C., and New York. The geographic spread of the sites captured a range of different climatic conditions. They also used a variety of child and adult outpatient settings.

Groups of study participants were randomly assigned to wear the N95 or a medical mask while carrying out their normal patient-oriented tasks. Researchers collected data during four flu seasons between 2011 and 2015 and examined the incidence of flu and acute respiratory viral illnesses in the almost 2,400  health care workers who completed the study. They took into account the participants’ flu vaccine status and required daily notes about symptoms in addition to lab tests.

“It was a huge study – the largest ever done on this issue in North America,” said senior author Trish Perl, M.D., Chief of University of Texas Southwestern Medical Center’s Division of Infectious Diseases and Geographic Medicine. The larger sample size allowed for a more rigorous analysis of statistical significance.

They found 207 laboratory-confirmed flu infections in the N95 user group versus 193 among medical mask wearers. There were also 2,734 cases of flu-like symptoms, laboratory-confirmed respiratory illnesses, and acute or laboratory-detected respiratory infections (where the worker may not have felt ill) in the N95 user group, compared with 3,039 such events among medical mask wearers. Statistically, these differences are insignificant.

“This provides us an opening to study the transmission of respiratory viruses in health care settings and develop new strategies to minimize infection risks,” Cummings said.

“The takeaway is that this study shows one type of protective equipment is not superior to the other,” Dr. Perl said. “Facilities have several options to provide protection to their staff – which include surgical masks – and can feel that staff are protected from seasonal influenza. Our study supports that in the outpatient setting there was no difference between the tested protections.”

Investigators included researchers at the University of Florida, University of Texas, CDC, Veterans Affairs Administration, Johns Hopkins, University of Colorado, Children’s Hospital Colorado and the University of Massachusetts.

The project was funded by the CDC, the Veterans Health Administration, and the Biomedical Advanced Research and Development Authority (BARDA), which is part of the U.S. Health and Human Services Department and was founded in the years after Sept. 11, 2001, to help secure the nation against biological and other threats.

By: DeLene Beeland