Here's a meta-study of 10 you can peruse... "In pooled analysis, we found no significant reduction in influenza transmission with the use of face masks (RR 0.7

Here's a meta-study of 10 you can peruse... "In pooled analysis, we found no significant reduction in influenza transmission with the use of face masks (RR 0.78, 95% CI 0.51–1.20; I2 = 30%, p = 0.25)" https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article