A US study reported “no significant difference in the effectiveness” of medical masks versus more expensive N95 respirators for prevention of influenza or other viral respiratory illness.
A study compared the ubiquitous surgical (or medical) mask, which costs about a dime, to a less commonly used respirator called an N95, which costs around $1. The study reported "no significant difference in the effectiveness" of medical masks vs N95 respirators for prevention of influenza or other viral respiratory illness.
"This study showed there is no difference in incidence of viral respiratory transmission among health care workers wearing the two types of protection," said Dr Trish Perl, chief of University of Texas Southwestern's division of infectious diseases and geographic medicine and the report's senior author. "This finding is important from a public policy standpoint because it informs about what should be recommended and what kind of protective apparel should be kept available for outbreaks."
Medical personnel – in particular nurses, doctors, and others with direct patient contact – are at risk when treating patients with contagious diseases such as influenza (flu). A large study conducted in a New York hospital system after the 2009 outbreak of H1N1, or swine flu, found almost 30 percent of health care workers in emergency departments contracted the disease themselves, Perl said.
During that pandemic, the US Centres for Disease Control and Prevention (CDC) recommended using the tighter-fitting N95 respirators, designed to fit closely over the nose and mouth and filter at least 95% of airborne particles, rather than the looser-fitting surgical masks routinely worn by health care workers, Perl said. But some facilities had trouble replenishing N95s as supplies were used.
In addition, there are concerns health care workers might be less vigilant about wearing the N95 respirators since many perceive them to be less comfortable than medical masks, such as making it harder to breathe and being warmer on the wearer's face. Earlier clinical studies comparing the masks and respirators yielded mixed results, said Perl, also a professor of internal medicine who holds the Jay P Sanford professorship in infectious diseases.
The study was performed at multiple medical settings in seven cities around the country, including Houston, Denver, Washington, and New York, by researchers at the University of Texas, the CDC, Johns Hopkins University, the University of Colorado, Children's Hospital Colorado, the University of Massachusetts, the University of Florida, and several Department of Veterans Affairs hospitals. Researchers collected data during four flu seasons between 2011 and 2015, examining the incidence of flu and acute respiratory illnesses in the almost 2,400 health care workers who completed the study.
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 US 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. "It was a huge and important study – the largest ever done on this issue in North America," Perl said.
In the end, 207 laboratory-confirmed influenza infections occurred in the N95 groups versus 193 among medical mask wearers, according to the report. In addition, there were 2,734 cases of influenza-like symptoms, laboratory-confirmed respiratory illnesses, and acute or laboratory-detected respiratory infections (where the worker may not have felt ill) in the N95 groups, compared with 3,039 such events among medical mask wearers.
"The takeaway is that this study shows one type of protective equipment is not superior to the other," she 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."
Perl said she expects more studies to arise from the data collected in this report; she now plans to investigate the dynamics of virus transmission to better understand how respiratory viruses are spread.
Importance: Clinical studies have been inconclusive about the effectiveness of N95 respirators and medical masks in preventing health care personnel (HCP) from acquiring workplace viral respiratory infections.
Objective: To compare the effect of N95 respirators vs medical masks for prevention of influenza and other viral respiratory infections among HCP.
Design, Setting, and Participants: A cluster randomized pragmatic effectiveness study conducted at 137 outpatient study sites at 7 US medical centers between September 2011 and May 2015, with final follow-up in June 2016. Each year for 4 years, during the 12-week period of peak viral respiratory illness, pairs of outpatient sites (clusters) within each center were matched and randomly assigned to the N95 respirator or medical mask groups.
Interventions: Overall, 1993 participants in 189 clusters were randomly assigned to wear N95 respirators (2512 HCP-seasons of observation) and 2058 in 191 clusters were randomly assigned to wear medical masks (2668 HCP-seasons) when near patients with respiratory illness.
Main Outcomes and Measures: The primary outcome was the incidence of laboratory-confirmed influenza. Secondary outcomes included incidence of acute respiratory illness, laboratory-detected respiratory infections, laboratory-confirmed respiratory illness, and influenzalike illness. Adherence to interventions was assessed.
Results: Among 2862 randomized participants (mean [SD] age, 43 [11.5] years; 2369 [82.8%]) women), 2371 completed the study and accounted for 5180 HCP-seasons. There were 207 laboratory-confirmed influenza infection events (8.2% of HCP-seasons) in the N95 respirator group and 193 (7.2% of HCP-seasons) in the medical mask group (difference, 1.0%, [95% CI, −0.5% to 2.5%]; P = .18) (adjusted odds ratio [OR], 1.18 [95% CI, 0.95-1.45]). There were 1556 acute respiratory illness events in the respirator group vs 1711 in the mask group (difference, −21.9 per 1000 HCP-seasons [95% CI, −48.2 to 4.4]; P = .10); 679 laboratory-detected respiratory infections in the respirator group vs 745 in the mask group (difference, −8.9 per 1000 HCP-seasons, [95% CI, −33.3 to 15.4]; P = .47); 371 laboratory-confirmed respiratory illness events in the respirator group vs 417 in the mask group (difference, −8.6 per 1000 HCP-seasons [95% CI, −28.2 to 10.9]; P = .39); and 128 influenzalike illness events in the respirator group vs 166 in the mask group (difference, −11.3 per 1000 HCP-seasons [95% CI, −23.8 to 1.3]; P = .08). In the respirator group, 89.4% of participants reported “always” or “sometimes” wearing their assigned devices vs 90.2% in the mask group.
Conclusions and Relevance: Among outpatient health care personnel, N95 respirators vs medical masks as worn by participants in this trial resulted in no significant difference in the incidence of laboratory-confirmed influenza.
Lewis J Radonovich, Michael S Simberkoff, Mary T Bessesen, Alexandria C Brown, Derek AT Cummings, Charlotte A Gaydos, Jenna G Los, Amanda E Krosche, Cynthia L Gibert, Geoffrey J Gorse, Ann-Christine Nyquist, Nicholas G Reich, Maria C Rodriguez-Barradas, Connie Savor Price, Trish M Perl
[link url="https://www.utsouthwestern.edu/newsroom/articles/year-2019/surgical-masks-virus-protection.html"]UT Southwestern Medical Centre material[/link]
[link url="https://jamanetwork.com/journals/jama/article-abstract/2749214"]JAMA abstract[/link]
[link url="https://jamanetwork.com/journals/jama/article-abstract/2749198"]JAMA editorial[/link]