The recommendation to wear surgical masks to supplement other public health measures did not reduce the SARS-CoV-2 infection rate among wearers by more than 50% in a community with modest infection rates, some degree of social distancing, and uncommon general mask use. The data were compatible with lesser degrees of self-protection.”

Bundgaard H, Bundgaard JS et al. 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. 18 November 2020: M20-6817. www.acpjournals.org/doi/10.7326/M20-6817. Epub ahead of print. PMID: 33205991; PMCID: PMC7707213.