PITTSBURGH—How effective are N95 respirators and medical masks in preventing healthcare personnel from acquiring workplace viral respiratory infections?

A study in JAMA sought to answer that question. Researchers from the National Personal Protective Technology Laboratory from the Centers for Disease Control and Prevention, with participants from VAMCs around the country, sought to compare the effect of N95 respirators vs. medical masks for prevention of influenza and other viral respiratory infections among HCP.1

The cluster randomized pragmatic effectiveness study was conducted at 137 outpatient study sites at seven U.S. medical centers between September 2011 and May 2015, with final follow-up in June 2016. Each year for four years, during the 12-week period of peak viral respiratory illness, pairs of outpatient sites (clusters) within each center were matched and randomly assigned to the N95 respirator or medical mask groups.

Researchers report that, overall, 1,993 participants in 189 clusters were randomly assigned to wear N95 respirators over 2,512 HCP-seasons of observation, while 2,058 in 191 clusters were randomly assigned to wear medical masks, representing 2,668 HCP-seasons) when near patients with respiratory illness.

Defined as the primary outcome was the incidence of laboratory-confirmed influenza. Secondary outcomes included incidence of acute respiratory illness, laboratory-detected respiratory infections, laboratory-confirmed respiratory illness and influenza-like illness.

The study team also assessed adherence to interventions. In the respirator group, 89.4% of participants reported “always” or “sometimes” wearing their assigned devices, compared to 90.2% in the mask group.

Results identified 207 laboratory-confirmed influenza infection events (8.2% of HCP-seasons) in the N95 respirator group and 193 (7.2% of HCP-seasons) in the medical mask group (difference, 1.0%, [95% CI, -0.5% to 2.5%]; P = .18) (adjusted odds ratio [OR], 1.18 [95% CI, 0.95-1.45]).

At the same time, there were:

  • 1,556 acute respiratory illness events in the respirator group vs. 1,711 in the mask group (difference, -21.9 per 1000 HCP-seasons [95% CI, -48.2 to 4.4]; P = .10);
  • 679 laboratory-detected respiratory infections in the respirator group vs. 745 in the mask group (difference, -8.9 per 1000 HCP-seasons, [95% CI, -33.3 to 15.4]; P = .47);
  • 371 laboratory-confirmed respiratory illness events in the respirator group vs. 417 in the mask group (difference, -8.6 per 1000 HCP-seasons [95% CI, -28.2 to 10.9]; P = .39); and
  • 128 influenza-like illness events in the respirator group vs. 166 in the mask group (difference, -11.3 per 1000 HCP-seasons [95% CI, -23.8 to 1.3]; P = .08).

“Among outpatient health care personnel, N95 respirators vs medical masks as worn by participants in this trial resulted in no significant difference in the incidence of laboratory-confirmed influenza,” the researchers concluded.

  1. Radonovich LJ Jr, Simberkoff MS, Bessesen MT, Brown AC, et. Al. ResPECT investigators. N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial. JAMA. 2019 Sep 3;322(9):824-833. doi:10.1001/jama.2019.11645. PubMed PMID: 31479137; PubMed Central PMCID: PMC6724169.