Date: March 4th, 2020

Reference: Radonovich et al. N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel. A Randomized Clinical Trial. JAMA 2019 The Respiratory Protection Effectiveness Clinical Trial (ResPECT)

Guest Skeptics: Dr. Christopher Patey is an Assistant Professor with Memorial University Medical School in St. John’s, Newfoundland Canada. Over the past seventeen years he has practiced as a rural emergency and family physician and Clinical Chief of Emergency at Carbonear Hospital.

Paul Norman is a registered nurse working as a frontline emergency nurse in Eastern Health, Newfoundland, Canada. Paul has greater than ten years of experience working in Emergency Nursing and Critical Care. His focus is implementation of LEAN strategies, quality and process improvement. Paul’s work has been extended to reach emergency services throughout Canada and he has contributed on many platforms including local, regional, provincial and national speaking engagements.

Disclaimers: This episode is about influenza not coronavirus (Covid-19)

Dr. Patey’s Disclaimer: I am not an expert on PPE (Personal Protective Equipment), Influenza/HINI/Coronavirus, Journal Reviews or Emergency Department management of pandemics.

Paul Norman’s Disclaimer: We (Dr. Patey and I) are experts on asking questions on the frontline of a Rural Emergency Department to ensure quality, and most importantly, effective patient care.

Dr. Ken Milne’s Disclaimer: I am an expert on critical appraisal but do not know what mask (if any) is best for preventing the Covid-19 virus.

I think we can all agree on a few general recommendation: Get a flu shot if possible, wash your hands well (at least 20 seconds with soap and water), try not to touch your face, avoid people who are sick, stay home if you are feeling ill, cough into a tissue and throw it out immediately or cough into your elbow, disinfect objects or surfaces with a regular household cleaning wipe or spray, people who are well do not need to wear a facemask, people who are feeling ill should wear a facemask, and reach out to your local health authority if you think you might have the COVID-19.

Covid-19 Information:

This story is evolving quickly, and people should go to official websites to get the latest update on the Cover-19 situation:

Case: With the potential global impact of the coronavirus (COVID-19) and our rural emergency departments (ED) having an extremely low compliance rate for N95 mask fit testing, our ED administration sends an urgent request for everyone to have N95 mask testing as soon as possible (ASAP). The urgent email also request shaving facial hair. You wonder about the evidence supporting the initiative and if there is any recent evidence surrounding N95 masks usage for preventing health care workers getting acute respiratory illnesses.

Background: Many hospitals had their health care workers fitted with N95 masks in response to the 2009 H1N1 pandemic. The N95 masks were known to prevent small particles and therefore thought to be more effective. What was not known is whether or not this better effectiveness would translate into less viral respiratory infections acquired in hospital compared to regular disposable surgical medical masks. In other words, would N95 masks have a healthcare provider-oriented outcome.

When it appeared that the transmission of the pandemic H1N1 was not different from seasonal influenza the recommendation for medical masks in most settings was reinstated.

With the potential for an epidemic/pandemic outbreak of coronovirus, there is the demand for increased vigilance in preventive measures to prevent and contain the outbreak of this communicable disease.

There have been a number of other studies discussing masks in preventing influenza spread:

  • Loeb et al 2009 did a non-inferiority trial of surgical masks vs. N95 respirator masks for preventing flu in Ontario nurses working at tertiary care hospitals. They concluded surgical masks were non-inferior.
  • MacIntyre et al 2009 did a cluster RCT on the use of face masks to control for respiratory virus transmission in households. They found face masks were unlikely to be an effective policy for seasonal respiratory diseases. This was in part because <50% of participants had mask adherence. Those who wore the mask did have a statistically significant reduction in clinical infection.
  • MacIntyre et al 2011 published another study in the same year comparing efficacy non-face masks to fit tested and non-fit tested N95 respiratory mask in preventing respiratory infections in hospital workers in China. The results showed a significant decrease in respiratory illnesses including influenza. The authors did cautioned readers that the trial may have been underpowered.
  • Smith et al CMAJ 2016 did a systematic review and meta-analysis on this topic. The authors concluded: “Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.”

Clinical Question: Are N95 masks superior in preventing flu or flu like illnesses in hospital workers compared to medical masks?

Reference: Radonovich et al. N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel. A Randomized Clinical Trial. JAMA 2019 The Respiratory Protection Effectiveness Clinical Trial (ResPECT)

  • Population: Full-time hospital employees defined as providing at least 24hrs of direct patient care a week. Participants were instructed to wear their assigned protective devices during a 12-week period (intervention period) during which the incidence of viral respiratory illness was expected to be highest that year developed by the ALERT algorithm. This was for 48 weeks of intervention spanning four consecutive viral respiratory seasons.
  • Intervention: N95 respirator mask. Employees were told to wear their masks when six feet (two meters) from a person suspected or confirmed of having a respiratory illness.
  • Control: Medical mask
  • Outcomes:
    • Primary Outcome: Incidence of laboratory-confirmed influenza.
    • Secondary Outcomes: Incidence of acute respiratory illness, laboratory-detected respiratory infections, laboratory-confirmed respiratory illness, and influenza like illness. Adherence to interventions was also assessed.

Authors’ Conclusions: Among outpatient healthcare 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.

Quality Checklist for Randomized Clinical Trials:

  1. The study population included or focused on those in the emergency department. No
  2. The patients were adequately randomized. Yes
  3. The randomization process was concealed. Yes
  4. The patients were analyzed in the groups to which they were randomized. Yes
  5. The study patients were recruited consecutively (i.e. no selection bias). Yes
  6. The patients in both groups were similar with respect to prognostic factors. Yes
  7. All participants (patients, clinicians, outcome assessors) were unaware of group allocation. No
  8. All groups were treated equally except for the intervention. Yes
  9. Follow-up was complete (i.e. at least 80% for both groups). Yes
  10. All patient-important outcomes were considered. Unsure
  11. The treatment effect was large enough and precise enough to be clinically significant. No

Key Results: This study was conducted at seven medical centers and 137 outpatient sites over four years (2011-2015) during the 3-month flu season. They enrolled 2,862 full time employees with a mean age of 43 years and 84% female. Nurses made up 41% of the cohort and less than 10% were physicians.

No statistical difference in the laboratory-confirmed influenza between an N95 mask and a medical mask.

  • Primary Outcome: Laboratory-confirmed influenza
    • 8.2% N95 respirator group and 7.2% medical mask group (difference, 1.0%, [95% CI: −0.5% to 2.5%]; P = 0.18)
    • Adjusted odds ratio (OR) was 1.18 (95% CI: 0.95 to 1.45)
  • Secondary Outcomes: No statistical difference in any of the secondary outcomes using an intention-to-treat (ITT) or per-protocol (PP) analysis.

Self-reported wearing of the mask “always” or “sometimes” was about 90% in both groups.

  1. Self-Reporting: Health care workers self-reported any illness. This could have resulted in under or over reporting of being sick. Adherence to mask use was also self-reported. Of those reporting, 90% said they wore the mask always or sometimes. However, almost one-third in each group did not even report adherence. This further limits the interpretation of the results.
  2. Lack of Physicians: Less than 10% of the cohort were physicians. This means we have much less data on this group of individuals. I also suspect physicians were less likely to follow mask recommendations. Unfortunately, the supplemental material did not break down how many physicians were in the physician, physician trainees or advanced practitioners’ cohort.
  3. Outside of Work: Participants were not required to use the masks outside of their work setting. Employees had to have at least 24 hours/week of direct patient care to be included in the study. However, more time would have been spent out of the hospital/clinic setting. These outside influences/exposures could have an impact on the results.
  4. Patient-Oriented Outcome: This study was focused on the employees. While there was no significant difference in the health care worker getting ill it would have been great to know if it had any impact on the patients’ well-being.
  5. Cost: N95 respiratory masks are more expensive than medical masks. First, we must determine if the intervention works. This study does not support a benefit for hospital employees. If it did show a benefit to them or more importantly the patients, then we could decide if the cost was worth any efficacy. Without good evidence of benefit, we should consider putting resources towards things that do have evidence of efficacy like vaccination programs and hand washing initiatives.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We generally agree with the authors’ conclusions.

SGEM Bottom Line: There appears to be no statistical advantage to the N95 respiratory mask over surgical or medical mask for hospital employees in preventing flu or flu like illnesses.

Dr. Patey

Case Resolution: You respond to the email from the nursing administration to follow hospital guidelines, continue N95 mask testing and to follow hospital policies. However, I think it is important to stress to all staff to get their flu shot, consistently wash their hands, stop touching their face and wear a mask if a patient has suspected or confirmed respiratory illness.

Paul Norman

Clinical Application: This study will increase my use of a mask (medical mask or N95) with all suspected patients arriving to an ED or outpatient setting. We should also focus on things that have been demonstrated to have a benefit like vaccination and good hand washing. 

What Do I Tell the Staff?  Get immunized against influenza, wash your hands well and often, try not to touch your face and wear a mask when around patients who have suspected or confirmed respiratory illness. 

Keener Kontest: Last weeks’ winner was Rodney Hodge from Bayswater north, Australia. He knew the original Crayola box introduced in 1903 contained eight colours (red, orange, yellow, green, blue, violet, brown, and black) and it sold for only a nickel.

Listen to the SGEM podcast to hear this weeks’ question. Send your answer to with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine