Controversial Finding: In Real-World Clinical Practice, N95 Respirators no more Protective than Surgical Masks

July 8th, 2015

In a study certain to stir controversy, researchers in Canada report that N95 respirators were no better than surgical masks in preventing respiratory infections in healthcare workers in clinical settings.

“Although N95 respirators compared to surgical masks may have a protective advantage in laboratory evaluations, our meta-analysis identified that data from clinical settings does not provide evidence that N95 respirators offer superior protection for healthcare workers against transmissible acute respiratory infections in a clinical setting,” the authors reported recently in Victoria, British Columbia, at the Infection Prevention and Control (IPAC) Canada 2015 National Education Conference.¹

Saying the paper had been submitted for publication, lead author Jeffrey Smith, MSc, of Public Health Ontario, declined a request for comment on the study. As to factors related to the findings, they were not cited in the abstract, but it's known that N95s will not be full protective if they have not been properly fit-tested, worn correctly and in compliance as warranted by the situation. The respirators are often recommended for emerging pathogens like MERS.

The authors synthesized the available clinical and surrogate exposure data comparing N95 respirators to surgical masks for the prevention of transmissible acute respiratory infections. They searched the peer reviewed literature between January 1990 and December 2014. For clinical studies, they included English-language randomized controlled trials (RCTs), cohort studies, and case-control studies that included data on N95 respirators or equivalent and surgical masks used to prevent acute respiratory infections. The primary outcome for the meta-analysis was laboratory-confirmed respiratory infection. Secondary outcomes for the meta-analysis included influenza-like illness and workplace absenteeism. Surrogate exposure studies were examined and summarized, but not included in meta-analysis. Outcomes related to surrogate exposure studies were filter penetration, face-seal leakage, and total inward leakage.

Overall, six studies were included in the meta-analysis, which found no significant difference in associated risk of laboratory-confirmed respiratory infection when N95 respirators and surgical masks were compared in RCTs. Similarly, there was no significant difference in associated risk of influenza-like illness or workplace absenteeism when N95 respirators and surgical masks were compared in clinical trials, they concluded.

“Twenty-three additional surrogate exposure studies were included,” they note. “These studies in general demonstrated that N95 respirators have less filter penetration, face-seal leakage, and total inward leakage than surgical masks.”

REFERENCE

1. Smith J, MacDougall C, Johnstone J, et al. Respirators versus surgical masks to protect health care workers from acute respiratory infections: A systemic review and meta-analysis. Infection Prevention and Control (IPAC) Canada 2015 National Education Conference. Victoria, B.C. June 15-16, 2015. n