Surgical mask vs N95 respirator for preventing influenza among health care workers: a randomized trial.
BACKGROUND
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.


METHODS
Noninferiority randomized controlled trial of 446 nurses in emergency departments, medical units, and pediatric units in 8 tertiary care Ontario hospitals.


METHODS
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.


METHODS
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%.


CONCLUSIONS
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.


BACKGROUND
clinicaltrials.gov Identifier: NCT00756574
Loeb
Mark
M
Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
Dafoe
Nancy
N
Mahony
James
J
John
Michael
M
Sarabia
Alicia
A
Glavin
Verne
V
Webby
Richard
R
Smieja
Marek
M
Earn
David J D
DJ
Chong
Sylvia
S
Webb
Ashley
A
Walter
Stephen D
SD
D000328:Adult; D003428:Cross Infection / Q000517:prevention & control / Q000635:transmission; D005260:Female; D006801:Humans; D017758:Infectious Disease Transmission, Patient-to-Professional / Q000517:prevention & control*; D007251:Influenza, Human / Q000175:diagnosis / Q000517:prevention & control* / Q000635:transmission*; D008297:Male; D008397:Masks; D008875:Middle Aged; D009726:Nurses; D009784:Occupational Diseases / Q000517:prevention & control; D009975:Orthomyxoviridae / Q000302:isolation & purification; D012328:RNA Viruses / Q000302:isolation & purification; D012134:Respiratory Protective Devices; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult