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Loeb M, Dafoe N, Mahony J, et al. Surgical mask vs N95 respirator for preventing influenza among health care workers: a randomized trial. JAMA. 2009 Nov 4;302(17):1865-71. Epub 2009 Oct 1. (Original) PMID: 19797474
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Clinical Evidence Topic: Influenza
DISCIPLINE	RELEVANCE TO PRACTICE	IS THIS NEWS?
Emergency Medicine
Hospital Doctor/Hospitalists
Infectious Disease
Internal Medicine
Occupational and Environmental Health

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Abstract
CONTEXT: Data about the effectiveness of the surgical mask compared with the N95 respirator for protecting health care workers against influenza are sparse. Given the likelihood that N95 respirators will be in short supply during a pandemic and not available in many countries, knowing the effectiveness of the surgical mask is of public health importance. OBJECTIVE: To compare the surgical mask with the N95 respirator in protecting health care workers against influenza. DESIGN, SETTING, AND PARTICIPANTS: Noninferiority randomized controlled trial of 446 nurses in emergency departments, medical units, and pediatric units in 8 tertiary care Ontario hospitals. INTERVENTION: Assignment to either a fit-tested N95 respirator or a surgical mask when providing care to patients with febrile respiratory illness during the 2008-2009 influenza season. MAIN OUTCOME MEASURES: The primary outcome was laboratory-confirmed influenza measured by polymerase chain reaction or a 4-fold rise in hemagglutinin titers. Effectiveness of the surgical mask was assessed as noninferiority of the surgical mask compared with the N95 respirator. The criterion for noninferiority was met if the lower limit of the 95% confidence interval (CI) for the reduction in incidence (N95 respirator minus surgical group) was greater than -9%. RESULTS: Between September 23, 2008, and December 8, 2008, 478 nurses were assessed for eligibility and 446 nurses were enrolled and randomly assigned the intervention; 225 were allocated to receive surgical masks and 221 to N95 respirators. Influenza infection occurred in 50 nurses (23.6%) in the surgical mask group and in 48 (22.9%) in the N95 respirator group (absolute risk difference, -0.73%; 95% CI, -8.8% to 7.3%; P = .86), the lower confidence limit being inside the noninferiority limit of -9%. CONCLUSION: Among nurses in Ontario tertiary care hospitals, use of a surgical mask compared with an N95 respirator resulted in noninferior rates of laboratory-confirmed influenza. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00756574

Abstract

CONTEXT: Data about the effectiveness of the surgical mask compared with the N95 respirator for protecting health care workers against influenza are sparse. Given the likelihood that N95 respirators will be in short supply during a pandemic and not available in many countries, knowing the effectiveness of the surgical mask is of public health importance.
OBJECTIVE: To compare the surgical mask with the N95 respirator in protecting health care workers against influenza. DESIGN, SETTING, AND PARTICIPANTS: Noninferiority randomized controlled trial of 446 nurses in emergency departments, medical units, and pediatric units in 8 tertiary care Ontario hospitals. INTERVENTION: Assignment to either a fit-tested N95 respirator or a surgical mask when providing care to patients with febrile respiratory illness during the 2008-2009 influenza season. MAIN OUTCOME MEASURES: The primary outcome was laboratory-confirmed influenza measured by polymerase chain reaction or a 4-fold rise in hemagglutinin titers. Effectiveness of the surgical mask was assessed as noninferiority of the surgical mask compared with the N95 respirator. The criterion for noninferiority was met if the lower limit of the 95% confidence interval (CI) for the reduction in incidence (N95 respirator minus surgical group) was greater than -9%.
RESULTS: Between September 23, 2008, and December 8, 2008, 478 nurses were assessed for eligibility and 446 nurses were enrolled and randomly assigned the intervention; 225 were allocated to receive surgical masks and 221 to N95 respirators. Influenza infection occurred in 50 nurses (23.6%) in the surgical mask group and in 48 (22.9%) in the N95 respirator group (absolute risk difference, -0.73%; 95% CI, -8.8% to 7.3%; P = .86), the lower confidence limit being inside the noninferiority limit of -9%.
CONCLUSION: Among nurses in Ontario tertiary care hospitals, use of a surgical mask compared with an N95 respirator resulted in noninferior rates of laboratory-confirmed influenza. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00756574

Comments from Clinical Raters
Infectious Disease The Centers for Disease Control should read this, as their guidance is not evidence-based at this time.
Infectious Disease A very important study that suggests that surgical masks are adequate for influenza.
Internal Medicine Excellent topic area - one of a multitude of non-drug interventions that affect us everyday.
Internal Medicine Hard not to favor highlighting this article since this issue - about the use of N95 masks - is prominent within the hospital, and this is a trial.
Occupational and Environmental Health Very timely, however, there are other recent studies drawing the opposite conclusion. One obvious weakness is that the nurses may well have contacted influenza in the community, not in their workplace.

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