Influenza and other respiratory viruses 2017 08 11() doi 10.1111/irv.12474
We aim to examine the efficacy of medical masks and respirators in protecting against respiratory infections using pooled data from two homogenous randomised control clinical trials (RCTs).
The data collected on 3591 subjects in two similar RCTs conducted in Beijing China, which examined the same infection outcomes, were pooled. Four interventions were compared; a) continuous N95 respirator use, b) targeted N95 respirator use, c) medical mask use and, d) control arm. The outcomes were laboratory-confirmed viral respiratory infection, influenza A or B, laboratory-confirmed bacterial colonization, and pathogens grouped by mode of transmission.
Rates of all outcomes were consistently lower in the continuous N95 and/or targeted N95 arms. In adjusted analysis, rates of laboratory-confirmed bacterial colonization (RR 0.33, 95% CI 0.21-0.51), laboratory-confirmed viral infections (RR 0.46, 95% CI 0.23-0.91), and droplet transmitting infections (RR 0.26, 95% CI 0.16-0.42) were significantly lower in the continuous N95 arm. Laboratory-confirmed influenza was also lowest in the continuous N95 arm (RR 0.34, 95% CI 0.10-1.11) but the difference was not statistically significant. Rates of laboratory-confirmed bacterial colonization (RR 0.54, 95% CI 0.33-0.87), and droplet transmitting infections (RR 0.43, 95% CI 0.25-0.72) were also lower in the targeted N95 arm, but not in medical mask arm.
The results suggest that classification of infections into droplet versus airborne transmission is an oversimplification. Most guidelines recommend masks for infections spread by droplets. N95 respirators, as "air borne precaution", could provide superior protection for droplet transmitting infections, which should be reflected in infection control guidelines for occupational health and safety. This article is protected by copyright. All rights reserved.