There were several, but here's one. There was one earlier in theyear that I can't find that used weasle words like "Might" be helpful, and "should" provide "some" protection...but I didn't find that right away.
Disposable medical masks (also known as surgical masks) are loose-fitting devices that were designed to be worn by medical personnel to protect accidental contamination of patient wounds, and to protect the wearer against splashes or sprays of bodily fluids (36). There is limited evidence for their effectiveness in preventing influenza virus transmission either when worn by the infected person for source control or when worn by uninfected persons to reduce exposure. Our systematic review found no significant effect of face masks on transmission of laboratory-confirmed influenza.
https://wwwnc.cdc.gov/eid/article/15/2/08-1167_article
There were several, but here's one. There was one earlier in theyear that I can't find that used weasle words like "Might" be helpful, and "should" provide "some" protection...but I didn't find that right away.
https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article
Disposable medical masks (also known as surgical masks) are loose-fitting devices that were designed to be worn by medical personnel to protect accidental contamination of patient wounds, and to protect the wearer against splashes or sprays of bodily fluids (36). There is limited evidence for their effectiveness in preventing influenza virus transmission either when worn by the infected person for source control or when worn by uninfected persons to reduce exposure. Our systematic review found no significant effect of face masks on transmission of laboratory-confirmed influenza.
I this this is it but there could be more https://www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6936a5-H.pdf
Following