Efficacy of face masks and respirators in preventing upper respiratory tract bacterial colonization and co-infection in hospital healthcare workers

The rate of bacterial colonization was 2.8% in the N95 group (p = 0.02), 5.3% among medical mask users (p < 0.01) and 7.5% among the controls (p = 0.16). N95 respirators were significantly protective (adjusted RR 0.34, 95% CI: 0.21–0.56) against bacterial colonization. Co-infections of two bacteria or a virus and bacteria occurred in up to 3.7% of HCWs, and were significantly lower in the N95 arm.