National Library of Medicine: Two systematic reviews on masks
“Two randomised controlled trials were included involving a total of 1453 patients. In a small trial there was a trend towards masks being associated with fewer infections, whereas in alLarge trial there was no difference in infection rates between the masked and unmasked group. Neither trial accounted for cluster randomisation in the analysis.”
“None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection. Some evidence suggests that mask use is best undertaken as part of a package of personal protection especially hand hygiene.”