Purpose: This systematic review and meta-analysis assessed the effectiveness of personal respiratory protective equipment, such as medical masks and respirators, in protecting healthcare workers (HCWs) from respiratory infections.
Methods & Materials: The databases Pubmed, EMBASE and Web of Science were searched for relevant randomized controlled trials (RCTs) and observational studies with no language or time restrictions. We included published RCTs and observational studies assessing the effectiveness of medical masks and respirators in protecting HCWs from clinical or laboratory-confirmed respiratory outcomes. Editorials, press articles, reviews, guidelines, mathematical models, ongoing studies and non-peer-reviewed reports were excluded. Fixed- or random-effects model meta-analyses were conducted with appropriate combinations of RCTs or observational studies to calculate pooled risk ratios (RRs) or odds ratios (ORs), respectively. To facilitate an appropriate interpretation of the findings from our meta-analysis of observational studies, we calculated a range of plausible RRs for each summary OR, assuming a baseline risk of SARS-CoV infection ranging from 20% to 60%, as estimated from the available cohort studies.
Results: Six RCTs and twenty-three observational studies were included into this review. Meta-analysis of RCTs indicated a protective effect of masks and respirators against clinical respiratory illness (CRI) (RR=0.59; 95%CI: 0.46 to 0.77) and influenza-like illness (ILI) (RR=0.34; 95%CI: 0.14 to 0.82), but not laboratory-confirmed viral infection (VRI). Compared to masks, N95 respirators conferred superior protection against CRI (RR= 0.47; 95%CI= 0.36 to 0.62) and laboratory-confirmed bacterial infection (RR= 0.46; 95%CI= 0.34 to 0.62), but not ILI or VRI. In the meta-analysis of observational studies, there was fairly consistent evidence of a protective effect of both N95 respirators (OR= 0.12; 95%CI: 0.06 to 0.26) and medical masks (OR= 0.13; 95%CI: 0.03 to 0.62) against SARS. Evidence for a protective effect of masks or respirators against pandemic H1N1 influenza infection was not consistent.
Conclusion: Overall, this systematic review and meta-analysis supports the use of respiratory protection to prevent clinical symptoms of respiratory infection among HCWs when used consistently during non-epidemic scenarios. In addition, both N95 respirators and medical masks were effective against SARS, but not pandemic H1N1 influenza, although additional studies will be required to validate these findings.