Surgical Masks vs N95 Respirators Against H1N1

Data about the effectiveness of ordinary surgical masks as opposed to respirators in protecting health care workers against the 2009 H1N1 influenza virus are sparse.

Given high cost of N95 respirators and the likelihood that these 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.

An observational study among health care workers from April through August of 2009 at Tan Tock Seng Hospital in Singapore suggests that surgical masks are just as effective as respirators in this regard.

From June 19 to July 21, health care workers at the hospital wore N95 respirators in the emergency room and an H1N1 isolation area. From July 22 to Aug. 31, surgical masks were used by workers in these areas. The incidence of H1N1 among workers remained low during both periods. Although the study was observational, the findings suggest that surgical masks and respirators did not differ in their effectiveness in preventing hospital staff from acquiring H1N1.

This report of Brenda Ang et al confirms similar findings of Mark Loeb et al of McMaster University, Canada.

Data from their randomized controlled trial of 446 nurses in eight Ontario hospitals show that the incidence of laboratory-confirmed influenza was similar in nurses wearing the surgical mask and those wearing the N95 respirator. Surgical masks had an estimated efficacy within 1 percent of N95 respirators - surgical masks appeared to be no worse, within a prespecified margin, than N95 respirators in preventing influenza.

“What is more important than using high-filtration or respirator masks for known or suspected cases is to have a uniform policy, such as using surgical masks, when in close contact with all patients," said Brenda Ang. "This way, health care workers are protected from getting infected by patients not initially thought to have H1N1."

Both findings apply to routine care in routine health care settings and should not be generalized to settings where there is a high risk for aerosolization, such as intubation or bronchoscopy, where use of an N95 respirator would be prudent.

Journal Reference:

Brenda Ang, Bee Fong Poh, Mar Kyaw Win and Angela Chow. Surgical Masks for Protection of Health Care Personnel against Pandemic Novel Swine‐Origin Influenza A (H1N1)–2009: Results from an Observational Study. Clinical Infectious Diseases 2010;50:1011–1014

Loeb M, Dafoe N, Mahony J, John M, Sarabia A, Glavin V, Webby R, Smieja M, Earn DJ, Chong S, Webb A, Walter SD. Surgical mask vs N95 respirator for preventing influenza among health care workers: a randomized trial. JAMA. 2009 Nov 4;302(17):1865-71.