Assessing the Impact of Mask Mandates on SARS-CoV-2 Transmission: A Case Study of Utah

Background Throughout the COVID-19 pandemic, the effectiveness of face masks mandates has been intensely debated. Many methods have been used to demonstrate mask effectiveness, including one that compares the change in reproduction number following implementing and removing face mask mandates 1 . Methods Using data from Utah, we calculated the effect of mask mandates (E Fm ) in each local health district from before and after three key mandates: the Salt Lake and Summit County (SLSC) mask mandates enacted; the Utah statewide mask mandate enacted; and the Utah statewide mandate was lifted. Results We found that most counties had a reduction in the growth rate of cases following the mandates. There were reductions in E Fm in many counties after the introduction of the SLSC mask mandates and a more widespread reduction in E Fm across the state following the statewide mandate. Lifting the mandates, many counties across the states saw an increase in E Fm . Conclusion Our data show mask mandates were an effective way to reduce transmission both within the jurisdiction they were enacted and in neighboring jurisdictions. We provide evidence to support mask mandates as a way to prevent transmission to be better equipped to respond to future pandemics.