title: A cluster randomized clinical trial comparing fit-tested and non-fit-tested N95 respirators to medical masks to prevent respiratory virus infection in health care workers.
abstract: BACKGROUND
  We compared the efficacy of medical masks, N95 respirators (fit tested and non fit tested), in health care workers (HCWs).
  
  
  METHODS
  A cluster randomized clinical trial (RCT) of 1441 HCWs in 15 Beijing hospitals was performed during the 2008/2009 winter. Participants wore masks or respirators during the entire work shift for 4 weeks. Outcomes included clinical respiratory illness (CRI), influenza-like illness (ILI), laboratory-confirmed respiratory virus infection and influenza. A convenience no-mask/respirator group of 481 health workers from nine hospitals was compared.
  
  
  RESULTS
  The rates of CRI (3·9% versus 6·7%), ILI (0·3% versus 0·6%), laboratory-confirmed respiratory virus (1·4% versus 2·6%) and influenza (0·3% versus 1%) infection were consistently lower for the N95 group compared to medical masks. By intention-to-treat analysis, when P values were adjusted for clustering, non-fit-tested N95 respirators were significantly more protective than medical masks against CRI, but no other outcomes were significant. The rates of all outcomes were higher in the convenience no-mask group compared to the intervention arms. There was no significant difference in outcomes between the N95 arms with and without fit testing. Rates of fit test failure were low. In a post hoc analysis adjusted for potential confounders, N95 masks and hospital level were significant, but medical masks, vaccination, handwashing and high-risk procedures were not.
  
  
  CONCLUSIONS
  Rates of infection in the medical mask group were double that in the N95 group. A benefit of respirators is suggested but would need to be confirmed by a larger trial, as this study may have been underpowered. The finding on fit testing is specific to the type of respirator used in the study and cannot be generalized to other respirators.
  
  
  BACKGROUND
  Australian New Zealand Clinical Trials Registry (ANZCTR), ACTRN: ACTRN12609000257268 (http://www.anzctr.org.au).
authors.affiliation: School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Sydney, Australia. r.macintyre@unsw.edu.au
authors.forename: Chandini Raina
authors.initials: CR
authors.lastname: MacIntyre
authors.forename: Quanyi
authors.initials: Q
authors.lastname: Wang
authors.forename: Simon
authors.initials: S
authors.lastname: Cauchemez
authors.forename: Holly
authors.initials: H
authors.lastname: Seale
authors.forename: Dominic E
authors.initials: DE
authors.lastname: Dwyer
authors.forename: Peng
authors.initials: P
authors.lastname: Yang
authors.forename: Weixian
authors.initials: W
authors.lastname: Shi
authors.forename: Zhanhai
authors.initials: Z
authors.lastname: Gao
authors.forename: Xinghuo
authors.initials: X
authors.lastname: Pang
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Duan
authors.forename: Bayzidur
authors.initials: B
authors.lastname: Rahman
authors.forename: Neil
authors.initials: N
authors.lastname: Ferguson
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D017053:Infection Control; D008297:Male; D008397:Masks / Q000706:statistics & numerical data*; D016273:Occupational Exposure / Q000517:prevention & control* / Q000706:statistics & numerical data; D010564:Personnel, Hospital / Q000706:statistics & numerical data*; D011446:Prospective Studies; D012134:Respiratory Protective Devices / Q000706:statistics & numerical data*; D012141:Respiratory Tract Infections / Q000517:prevention & control* / Q000635:transmission / Q000821:virology