Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers : A Randomized Controlled Trial.
Ann Intern Med. 2021 Mar;174(3):335-343. doi: 10.7326/M20-6817. Epub 2020 Nov 18.
Ann Intern Med. 2021.
PMID:33205991
Free PMC article.
Clinical Trial.