N95 respirator and surgical mask are similarly protective against influenza

Clinical question How effective is the surgical mask compared to the N95 respirator in protecting health care workers against influenza?

Bottom line Laboratory-confirmed influenza occurred with similar incidence among nurses wearing a fit-tested N95 respirator compared with a standard surgical mask when caring for patients with febrile respiratory illness. Given the increased expense and greater discomfort with use of the N95 respirator compared with the surgical mask, this information should be very helpful for the coming influenza season. (Level of evidence = 1b)

Synopsis Real world evidence comparing different respiratory protective devices is sparse. These investigators randomized (concealed allocation assignment) 446 nurses working full time in emergency departments, medical units, and pediatric units from eight medical centers in Canada to either a fit-tested N95 respirator or surgical mask when providing care within one meter of patients with febrile respiratory illness. The primary outcome measured was laboratory-confirmed influenza. Personnel conducting confirmatory testing for influenza illness remained blind to intervention group assignments. Study subjects wore gloves and gowns when caring for patients with suspected infection. About 30% in each group received influenza vaccine during the study year. Complete follow-up occurred for more than 90% of participants. Using intention-to-treat analysis, laboratory-confirmed influenza occurred with similar incidence in both the surgical mask and N95 respirator group (23.6% vs 22.9%, respectively). In addition, there was a nonsignificant trend for an increased incidence of the specific pandemic H1N1 swine influenza strain in the N95 respirator group compared with the surgical mask group (11.9% vs 8.0%). Using per-protocol analysis with only data from subjects with complete follow-up there was still no significant difference in influenza illness between the two intervention groups. The study was 80% powered to detect a 10% risk reduction with the N95 respirator.

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;302(17):1865-1871. doi:10.1001/jama.2009.1466. Published October 1, 2009.