A randomized clinical trial of three options for N95 respirators and medical masks in health workers

Am J Respir Crit Care Med. 2013 May 1;187(9):960-6. doi: 10.1164/rccm.201207-1164OC.


Rationale: We compared three policy options for the use of medical masks and N95 respirators in healthcare workers (HCWs).

Objectives: A cluster randomized clinical trial of 1,669 hospital-based HCWs in Beijing, China in the winter of 2009-2010.

Methods: Participants were randomized to medical masks, N95 respirators, or targeted use of N95 respirators while doing high-risk procedures or barrier nursing. Outcomes included clinical respiratory illness (CRI) and laboratory-confirmed respiratory pathogens in symptomatic subjects.

Measurements and main results: The rate of CRI was highest in the medical mask arm (98 of 572; 17%), followed by the targeted N95 arm (61 of 516; 11.8%), and the N95 arm (42 of 581; 7.2%) (P < 0.05). Bacterial respiratory tract colonization in subjects with CRI was highest in the medical mask arm (14.7%; 84 of 572), followed by the targeted N95 arm (10.1%; 52 of 516), and lowest in the N95 arm (6.2%; 36 of 581) (P = 0.02). After adjusting for confounders, only continuous use of N95 remained significant against CRI and bacterial colonization, and for just CRI compared with targeted N95 use. Targeted N95 use was not superior to medical masks.

Conclusions: Continuous use of N95 respirators was more efficacious against CRI than intermittent use of N95 or medical masks. Most policies for HCWs recommend use of medical masks alone or targeted N95 respirator use. Continuous use of N95s resulted in significantly lower rates of bacterial colonization, a novel finding that points to more research on the clinical significance of bacterial infection in symptomatic HCWs. This study provides further data to inform occupational policy options for HCWs. Clinical trial registered with Australian New Zealand Clinical Trials Registry http://www.anzctr.org.au (ACTRN 12609000778280).

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • China
  • Cluster Analysis
  • Female
  • Health Personnel*
  • Humans
  • Infection Control / instrumentation*
  • Kaplan-Meier Estimate
  • Male
  • Masks*
  • Middle Aged
  • Occupational Exposure / prevention & control*
  • Proportional Hazards Models
  • Respiratory Protective Devices*
  • Respiratory Tract Infections / microbiology
  • Respiratory Tract Infections / prevention & control*
  • Respiratory Tract Infections / transmission
  • Tertiary Care Centers / organization & administration