title: Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis.
abstract: BACKGROUND
  Conflicting recommendations exist related to which facial protection should be used by health care workers to prevent transmission of acute respiratory infections, including pandemic influenza. We performed a systematic review of both clinical and surrogate exposure data comparing N95 respirators and surgical masks for the prevention of transmissible acute respiratory infections.
  
  
  METHODS
  We searched various electronic databases and the grey literature for relevant studies published from January 1990 to December 2014. Randomized controlled trials (RCTs), cohort studies and case-control studies that included data on health care workers wearing N95 respirators and surgical masks to prevent acute respiratory infections were included in the meta-analysis. Surrogate exposure studies comparing N95 respirators and surgical masks using manikins or adult volunteers under simulated conditions were summarized separately. Outcomes from clinical studies were laboratory-confirmed respiratory infection, influenza-like illness and workplace absenteeism. Outcomes from surrogate exposure studies were filter penetration, face-seal leakage and total inward leakage.
  
  
  RESULTS
  We identified 6 clinical studies (3 RCTs, 1 cohort study and 2 case-control studies) and 23 surrogate exposure studies. In the meta-analysis of the clinical studies, we found no significant difference between N95 respirators and surgical masks in associated risk of (a) laboratory-confirmed respiratory infection (RCTs: odds ratio [OR] 0.89, 95% confidence interval [CI] 0.64-1.24; cohort study: OR 0.43, 95% CI 0.03-6.41; case-control studies: OR 0.91, 95% CI 0.25-3.36); (b) influenza-like illness (RCTs: OR 0.51, 95% CI 0.19-1.41); or (c) reported workplace absenteeism (RCT: OR 0.92, 95% CI 0.57-1.50). In the surrogate exposure studies, N95 respirators were associated with less filter penetration, less face-seal leakage and less total inward leakage under laboratory experimental conditions, compared with surgical masks.
  
  
  CONCLUSIONS
  Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.
authors.affiliation: Public Health Ontario (Smith, MacDougall, Johnstone, Copes, Schwartz, Garber); Department of Medicine (Johnstone), University of Toronto; Dalla Lana School of Public Health (Copes, Schwartz), University of Toronto, Toronto, Ont.; Department of Medicine (Garber), University of Ottawa, Ottawa, Ont.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Smith
authors.affiliation: Public Health Ontario (Smith, MacDougall, Johnstone, Copes, Schwartz, Garber); Department of Medicine (Johnstone), University of Toronto; Dalla Lana School of Public Health (Copes, Schwartz), University of Toronto, Toronto, Ont.; Department of Medicine (Garber), University of Ottawa, Ottawa, Ont.
authors.forename: Colin C
authors.initials: CC
authors.lastname: MacDougall
authors.affiliation: Public Health Ontario (Smith, MacDougall, Johnstone, Copes, Schwartz, Garber); Department of Medicine (Johnstone), University of Toronto; Dalla Lana School of Public Health (Copes, Schwartz), University of Toronto, Toronto, Ont.; Department of Medicine (Garber), University of Ottawa, Ottawa, Ont.
authors.forename: Jennie
authors.initials: J
authors.lastname: Johnstone
authors.affiliation: Public Health Ontario (Smith, MacDougall, Johnstone, Copes, Schwartz, Garber); Department of Medicine (Johnstone), University of Toronto; Dalla Lana School of Public Health (Copes, Schwartz), University of Toronto, Toronto, Ont.; Department of Medicine (Garber), University of Ottawa, Ottawa, Ont.
authors.forename: Ray A
authors.initials: RA
authors.lastname: Copes
authors.affiliation: Public Health Ontario (Smith, MacDougall, Johnstone, Copes, Schwartz, Garber); Department of Medicine (Johnstone), University of Toronto; Dalla Lana School of Public Health (Copes, Schwartz), University of Toronto, Toronto, Ont.; Department of Medicine (Garber), University of Ottawa, Ottawa, Ont.
authors.forename: Brian
authors.initials: B
authors.lastname: Schwartz
authors.affiliation: Public Health Ontario (Smith, MacDougall, Johnstone, Copes, Schwartz, Garber); Department of Medicine (Johnstone), University of Toronto; Dalla Lana School of Public Health (Copes, Schwartz), University of Toronto, Toronto, Ont.; Department of Medicine (Garber), University of Ottawa, Ottawa, Ont. gary.garber@oahpp.ca.
authors.forename: Gary E
authors.initials: GE
authors.lastname: Garber
mesh_terms: D003428:Cross Infection / Q000517:prevention & control*; D006801:Humans; D008397:Masks; D009784:Occupational Diseases / Q000517:prevention & control*; D016273:Occupational Exposure / Q000517:prevention & control*; D012134:Respiratory Protective Devices; D012141:Respiratory Tract Infections / Q000517:prevention & control*