Author (year): Chu (2020)
Title: Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis
Article ID (DOI or PMID or other): https://doi.org/10.1016/ S0140-6736(20)31142-9
URL: https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(20)31142-9.pdf

Risk factor category: Other
Risk factor description: Wearing face mask (Yes vs. No)
Outcome: COVID-19 (any condition)
Result: Relative risk: 0.019 (0.003-0.135) Univariate analysis