Association Between Universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers

Mass General Brigham (MGB) is the largest health care system in Massachusetts, with 12 hospitals and more than 75 000 employees. In March 2020, MGB implemented a multipronged infection reduction strategy involving systematic testing of symptomatic HCWs and universal masking of all HCWs and patients with surgical masks.This study assessed the association of hospital masking policies with the SARS-CoV-2 infection rate among HCWs.