Surgical Masks Work As Well as N95 Respirators Against Influenza, Study Says

HealthLeaders Media Staff, November 4, 2009

Despite concerns about shortages, cost, and practicality of N95 respirators recommended by the CDC to protect healthcare workers against influenza, a new report says surgical masks, which are cheaper and easier to use, work just as well.

"Infection occurred in 50 nurses (23.6%) in the surgical mask group and in 48 (22.9%) in the N95 respirator group," the authors wrote. They concluded that the incidence of laboratory-confirmed influenza was similar in nurses wearing the surgical masks and those wearing the N95 respirators.

The study, by Mark Loeb, MD, and colleagues at McMaster University in Ontario, Canada, is based on a trial of 446 nurses at eight Ontario tertiary care hospitals during the 2008-2009 winter influenza season. Roughly half (225) were assigned to wear surgical masks while 221 were to wear fit-tested N95 respirators.

The report was published today in the Journal of the American Medical Association.

The Ontario study does not resolve the issue by any means. The two groups were said to have equal rates of influenza vaccination and comparable numbers of household members had flu-like symptoms during the study period. The investigators did not compare the groups in terms of their hand hygiene practices, triage procedures or cough etiquette, which could have been influential. Only infection as opposed to illness was measured as the outcome.

In mid-October, the Centers for Disease Control and Prevention re-confirmed guidance that healthcare workers should use "respiratory protection that is at least as protective as a fit-tested disposable N95 respirator" when in close contact with patients with suspected or confirmed 2009 H1N1 influenza." As of yesterday, that guideline was still in place, according to a CDC spokesman.

Confusion about what to do has prevailed in the absence of hard data.

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