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Original Investigation
September 3, 2019

N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial

Author Affiliations
  • 1National Personal Protective Technology Laboratory, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Pittsburgh, Pennsylvania
  • 2Veterans Affairs New York Harbor Healthcare System, New York
  • 3New York University School of Medicine, New York
  • 4Veterans Affairs Eastern Colorado Healthcare System, Denver
  • 5University of Colorado School of Medicine, Aurora
  • 6University of Massachusetts, Amherst
  • 7University of Florida, Gainesville
  • 8Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
  • 9Johns Hopkins School of Medicine, Baltimore, Maryland
  • 10Weill Cornell Medicine, New York, New York
  • 11Veterans Affairs Medical Center, Washington, DC
  • 12George Washington University School of Medical and Health Sciences, Washington, DC
  • 13Veterans Affairs St Louis Healthcare System, St Louis, Missouri
  • 14St Louis University School of Medicine, St Louis, Missouri
  • 15Children’s Hospital Colorado, Aurora
  • 16Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas
  • 17Baylor College of Medicine, Houston, Texas
  • 18Denver Health Medical Center, Denver, Colorado
  • 19University of Texas Southwestern Medical Center, Dallas
JAMA. 2019;322(9):824-833. doi:10.1001/jama.2019.11645
Key Points

Question  Is the use of N95 respirators or medical masks more effective in preventing influenza infection among outpatient health care personnel in close contact with patients with suspected respiratory illness?

Findings  In this pragmatic, cluster randomized clinical trial involving 2862 health care personnel, there was no significant difference in the incidence of laboratory-confirmed influenza among health care personnel with the use of N95 respirators (8.2%) vs medical masks (7.2%).

Meaning  As worn by health care personnel in this trial, use of N95 respirators, compared with medical masks, in the outpatient setting resulted in no significant difference in the rates of laboratory-confirmed influenza.

Abstract

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.

Trial Registration  ClinicalTrials.gov Identifier: NCT01249625

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