Should Clinicians Use N95 Respirators to Prevent Respiratory Illness?

As respiratory virus season approaches, infection control measures will become increasingly important. Personal protective equipment (PPE) is one of the strongest tools in an infection preventionist’s arsenal against the spread of diseases. Respiratory virus season means that we tend to see an influx of cases of adenovirus, parainfluenza, and influenza, which amplifies the need for PPE.

For health care workers and those involved in the care of patients, the US Centers for Disease Control and Prevention (CDC) recommends use of facemasks while in the room with a patient with suspected or confirmed influenza. This would be considered Droplet precautions (ie using a surgical mask to prevent the spread of microorganisms that are spread by close contact to patients sneezing/coughing). On the other hand, the CDC recommends that in a situation involving avian influenza (H5N1, H7, N9 strains), or a case of pandemic influenza with severe symptoms, health care workers should not use a regular facemask, but rather an N95 mask or higher.

This distinction has, in my experience, often inspired conversation and event debate within the infectious disease and infection control community. For many, the question is simple — should health care workers also be wearing N95 masks when caring for patients with seasonal influenza? Investigators of a new study sought to address this very question and to determine if there was a difference in the prevention of seasonal influenza between those staff wearing N95 masks versus regular facemasks.

Studying roughly 4000 participants across 137 outpatient and 7 medical centers across the United States from September 2011 to May 2015, the researchers accumulated a considerable amount of data in this cluster-randomized pragmatic effectiveness study. The study team focused on the 12-week period considered to be the peak of respiratory virus season and matched/randomly assigned pairs of outpatient sites within each health center to either N95 respirators or regular facemasks.

During the study period, 1993 participants across 189 clusters wore N95 masks (2512 health care worker-seasons of observations) and 2058 participants across 191 clusters wore medical masks (2668 health care worker-seasons) during interactions with patients experiencing a respiratory illness.

Within the N95 mask group, there were 207 lab-confirmed influenza infections (8.2% of health care worker-seasons) and 193 within the facemask group, representing 7.2% of health care worker-seasons. The researchers noted that “there were 1556 acute respiratory illness events in the respirator group vs 1711 in the mask group”, and 679 lab-detected respiratory infections in the N95 group versus 745 in the mask group—neither of which were statistically significant. Roughly 90% of health care workers in both groups reported that they wore their masks “always” or “sometimes”.

Ultimately, when assessing the lab-confirmed respiratory illness events and influenza-like illness events across the groups, there was not a statistically significant relationship between kind of mask and rates of laboratory-confirmed influenza.

This study found that in outpatient settings, there is no difference between N95 respirators and regular facemasks when it comes to preventing influenza infections in health care workers. Since N95 masks require fit-testing for occupational health purposes and tend to cost more, this finding is particularly helpful for infection control efforts and employee compliance with isolation precautions in outpatient settings.