Surgical masks, N95 respirators offer similar protection against influenza transmission

Rates of laboratory-confirmed influenza were similar among health care providers who wore surgical masks compared with those who wore fit-tested N95 respirators while caring for febrile patients with respiratory illness, recently published data indicate.

Researchers from several sites in Canada and the United States randomly assigned 446 nurses at eight Ontario tertiary care hospitals to wear either a surgical mask (n=225) or an N95 respirator (n=221) between Sept. 23, 2008 and Dec. 8, 2008. During the study period, 50 nurses in the surgical mask group contracted laboratory-influenza compared with 48 in the N95 respirator group.

“Surgical masks had an estimated efficacy within 1% of N95 respirators in preventing influenza,” the researchers wrote.

Vaccination status was similar among the two groups, with about 30% of nurses in each having received 2008-2009 trivalent inactivated influenza vaccine.

“This is a tremendous addition to our body of knowledge on this issue,” Mark E. Rupp, MD, president of the Society for Healthcare Epidemiology of America and professor of infectious diseases at the University of Nebraska Medical Center, said in an interview. “Going with a simpler, more cost-efficient surgical mask that health care workers will be more compliant with makes more sense than something that is cumbersome, uncomfortable, more costly and no more effective in routine clinical situations.”

The study findings are in accordance with SHEA’s recommendations for managing novel H1N1 influenza, which are based on the knowledge that the novel virus behaves similarly to seasonal influenza, according to Rupp, who said N95 fit-tested respirators should be reserved for procedures more likely to generate aerosols, such as bronchoscopy or intubation.

This study's findings contradict results presented at the recent ICAAC meeting that indicated that N95 masks may be more effective at preventing influenza transmission than surgical masks.

“It’s understandable that health care workers are concerned about acquisition of influenza in the work place, but quite frankly the type of respiratory protection they use is way down on the list of infection control measures that they should be emphasizing,” Rupp said. Vaccination is the most effective way to protect both patients and those in the health care community, according to Rupp, who encourages vaccination once the H1N1 vaccine becomes available.

Other important infection control strategies include prompt recognition and triage of patients with flu-like illness, promoting cough etiquette, encouraging patients to wear a mask, promoting appropriate hand hygiene and excluding sick visitors and healthcare workers. – by Nicole Blazek

JAMA. 2009;302(17): published online ahead of print.