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Surgical Masks or N95 Respirators for the Flu?

In a randomized trial, surgical masks and N95 respirators provided healthcare workers with comparable protection against influenza.

How best to protect healthcare workers against influenza remains unresolved. During the 2008–2009 winter influenza season, investigators compared surgical masks with fit-tested N95 respirators in a randomized trial involving eight Ontario, Canada, tertiary care hospitals.

Participants were 446 nurses who provided care to patients with febrile respiratory illness while working in emergency departments or inpatient medical or pediatric units. Follow-up (including twice-weekly assessment for signs and symptoms of influenza, and laboratory testing of nasal specimens from participants with influenza-like illness) lasted from January 12 through April 23, 2009. Influenza-vaccination status was comparable between the nurses using surgical masks and those using N95 respirators (30.2% and 28.1%, respectively), as were rates of exposure to spouses/roommates (22.4% and 25.9%) or children (22.6% and 20.5%) with influenza-like illness.

The incidence of laboratory-confirmed influenza was similar between groups (23.6% and 22.9%). In addition, no significant between-group differences were noted in the incidence of influenza-like illness or infections with respiratory syncytial virus, metapneumovirus, parainfluenza viruses, rhinovirus-enterovirus, or coronaviruses.

Comment: That protection against multiple respiratory viruses was comparable between surgical masks and fit-tested N95 respirators is reassuring, given the far greater costs and logistical issues associated with N95 respirators. This study shows the distressingly low acceptance of influenza vaccination by healthcare workers and acknowledges the reality of exposure to influenza outside the workplace.

— Richard T. Ellison III, MD

Published in Journal Watch Infectious Diseases October 21, 2009

Citation(s):

Loeb M et al. Surgical mask vs N95 respirator for preventing influenza among health care workers: A randomized trial. JAMA 2009 Oct 1; [e-pub ahead of print]. (http://dx.doi.org/10.1001/jama.2009.1466)

Reader Remarks:

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• Surgical masks vs N95
  Marysia Meylan, self employed Epidemiologist, 21 Oct 2009 9:12 PM EST
  Medscape reported another study on the same subject recently: http://www.medscape.com/viewarticle/709003?sssdmh=dm1.530110&src=nldne&uac=118273EK
• Masks for flu protection
  Jo Deverill, 30 Oct 2009 10:18 PM EST
  Given that it is impossible to conduct a blinded RCT of masks vs no masks, there is in my opinion... [more]