https://www.google.com/search?client=safari&rls=en&q=do+mask...
The first result (for me) https://journals.plos.org/plosone/article?id=10.1371/journal... -- an observational study from June'21, shows what appears to be a 14% reduction in transmission, a 13% reduction in deaths, and a 7% reduction in hospitalization.
The second result https://www.pnas.org/doi/10.1073/pnas.2014564118 -- seems to be an epidemiological meta analysis from Jan'21. It cites a 70% reduction in infection for those that always wore surgical masks.
The third: https://www.cdc.gov/coronavirus/2019-ncov/science/science-br... -- seems to be a CDC review of 18 studies that seem to support efficacy, with a table concisely summarizing each studies results.
Fourth: https://www.healthaffairs.org/doi/10.1377/hlthaff.2021.01072 -- this one from Feb'22 compares 414 US counties both with and without mask mandates. Oddly, showed that the benefits were greatest to Republican counties that imposed mandates, where a 25% reduction was found in masked over similar unmasked counties.
Fifth: https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 -- this is an older one from June 2020 and compares states with and without mandates, and shows lower daily infections in states with mandates.
Sixth: https://med.stanford.edu/news/all-news/2021/09/surgical-mask...
