Are cloth masks a substitute to medical masks in reducing transmission and contamination? A systematic review.
Level 3 - non-randomized controlled study
Systematic review composed predominantly of in vitro laboratory studies (8 of 11) with limited human clinical trials (1 non-RCT, 1 RCT).
PubMed 33146319 · doi:10.1590/1807-3107bor-2020.vol34.0123
What was done
A systematic review was conducted across electronic databases without date or language restrictions to assess the efficiency of cloth masks against droplets and aerosols for the general population and healthcare workers. Risk of bias was evaluated using an adapted checklist for laboratory studies, ROBINS-I for non-randomized trials, and Cochrane RoB 2.0 for randomized trials. Evidence certainty was graded using GRADE. Eleven studies were included: eight laboratory-based studies, one non-randomized trial, and one randomized trial supported by laboratory data.
What was found
Only three fabrics demonstrated filtration efficiency > 90%: cotton/chiffon hybrid (95% CI 95.2 to 98.8), cotton/silk hybrid (95% CI 92.2 to 95.8), and cotton quilt (95% CI 94.2 to 97.8). Cloth masks had lower efficiency than medical masks and were not recommended for healthcare workers. A meta-analysis could not be performed due to high methodological heterogeneity, with overall evidence quality ranging from very low to moderate.
Why it matters
The review identifies specific multi-layer hybrid fabric combinations that maximize filtration when medical masks are unavailable, while emphasizing that cloth masks remain unsuitable substitutes in high-risk healthcare settings.
Limits
The included literature is predominantly bench/laboratory simulations rather than real-world clinical endpoints; high heterogeneity prevented meta-analysis; and evidence certainty ranged from very low to moderate.
Cited by
- supports Cloth face coverings filter out a portion of viral particles to reduce both outward transmission and inward exposure for the wearer.