Importance: Clinical studies have been inconclusive about the effectiveness of N95 respirators and medical masks in preventing health care personnel (HCP) from acquiring workplace viral respiratory infections.
Objective: To compare the effect of N95 respirators vs medical masks for prevention of influenza and other viral respiratory infections among HCP.
Design, Setting, And Participants: A cluster randomized pragmatic effectiveness study conducted at 137 outpatient study sites at 7 US medical centers between September 2011 and May 2015, with final follow-up in June 2016.