Who you callin' unethical?

Many of you have probably already seen the news articles about the Australian study on the effectiveness of surgical masks versus N95s for prevention of influenza. The lead author of this study was quoted as saying, “It would not be ethical to recommend surgical masks for health-care workers”.

That’s a bold statement, and wrong. Even if one posits the superiority of N95 masks over surgical masks for protection of health care workers against influenza, there is a very old ethics principle (attributed to Immanuel Kant) that “ought implies can.” And at this time, it is simply not feasible for all front line health care workers to don N95 masks for the entirety of their shifts (for many reasons, not the least of which is that there simply aren’t enough masks).

But this assumes that this single study is definitive. I understand it is to be published soon, but I am unaware at this point of the results of peer-review of this work.

In addition, there is another randomized trial that came to a different conclusion about the effectiveness of surgical masks versus N95s. The complete results of this study can found at this link (to see specific outcome differences one must scroll down and open those windows). I’ve pasted the abstract below, which was presented at the 26th International Congress on Chemotherapy and Infection in Toronto in June. Both studies will apparently be published in JAMA in the near future. Until then, I’d advise Dr. MacIntyre to tone down the rhetoric about what’s “ethical” as we all do our best to protect both patients and health care workers during this trying flu season.

Randomized Control Trial to Study the Efficacy of the Surgical Mask Versus the N95 Respirator to Prevent Influenza

Mark Loeb, MD, et al.

Context: Data about the effectiveness of the surgical mask compared to the N95 respirator for protecting healthcare 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.
Objectives: To compare the surgical mask to the N95 respirator in protecting healthcare workers against influenza.
Design: Non-inferiority randomized controlled trial Setting: Emergency departments, medical, and paediatric units in eight Ontario tertiary care hospitals.
Participants: 446 nurses
Interventions: 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 PCR or a four-fold rise in haemaglutinin titres. Effectiveness of the surgical mask was assessed as non-inferiority of the surgical mask compared to N95 respirator.
Findings: Between September, 2008, and January, 2009, 478 nurses were assessed for eligibility and 446 nurses from eight centres in Ontario were enrolled and randomly assigned the intervention; 225 were allocated to surgical masks and 221 to N95 respirators. Influenza infection occurred in 50 (23.6%) of nurses 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=0.86); the lower confidence limit being inside the non-inferiority limit of -9%.
Interpretation: The surgical mask was non-inferior to the N95 respirator for preventing influenza among healthcare workers.

ClinicalTrials.gov number NCT00756574.


  1. Swine flu is very dangerous disease. Its almost fatal. Like its is said, "Prevention Is Better Than Cure", one should cover face with mask to protect from swine flu virus. The N-95 masks are popular. It is basically a surface for entrapment of the virus from outside, so one should wash the mask on a regular basis followed by washing one’s hands and face. For more details on swine flu masks, refer N95 respirator


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