First 10EM - By Justin Morgenstern - December 12, 2022
The paper
Loeb M, Bartholomew A, Hashmi M, Tarhuni W, Hassany M, Youngster I, Somayaji R, Larios O, Kim J, Missaghi B, Vayalumkal JV, Mertz D, Chagla Z, Cividino M, Ali K, Mansour S, Castellucci LA, Frenette C, Parkes L, Downing M, Muller M, Glavin V, Newton J, Hookoom R, Leis JA, Kinross J, Smith S, Borhan S, Singh P, Pullenayegum E, Conly J. Medical Masks Versus N95 Respirators for Preventing COVID-19 Among Health Care Workers : A Randomized Trial. Ann Intern Med. 2022 Nov 29. doi: 10.7326/M22-1966. Epub ahead of print. PMID: 36442064 NCT04296643
Bottom line
This study is a mess, and I don’t think you should draw many conclusions from it. The best scientific guess, based on this addition of this trial to the existing literatures, is that there is a small benefit of N95s over surgical masks at preventing the transmission of respiratory infections, but the magnitude of that benefit will depend heavily on baseline risk at any given time.