N95 respirators versus medical masks in viral infections transmitted by inhalation

Mark Loeb, MD, MSc, is a professor in the Department of Pathology and Molecular Medicine and Department of Clinical Epidemiology and Biostatistics and director of the Division of Infectious Diseases at McMaster University.

Is it already known which are better in providing medical care to those infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): medical masks or N95 respirators? Should we recommend the use of N95 respirators by immunosuppressed patients in the setting of increased exposure to pathogens transmitted by inhalation, including SARS-CoV-2?

In terms of using medical masks or N95 respirators when providing care for patients with coronavirus disease 2019 (COVID-19), there’s only one randomized controlled trial, which we at McMaster did. We randomized >1000 health-care workers to either medical masks or N95 respirators, and essentially the difference was noninferiority. If we look at absolute risk estimates, the risk difference between the 2 was maybe a little >1%. So, a little >1% of a difference of increase in infection with the medical masks compared with the N95 respirators, but with confidence intervals that ranged from ~2.5% to 4.9%. So, not much of a difference in our study.

In terms of giving patients the N95 respirators, there’s no evidence and, as far as I know, no recommendations for this because there’s no evidence to support it. Very practically, the experience is that often patients will have challenges wearing N95 respirators or medical masks for long periods of time.