There have been many different attempts to measure the efficacy of mask mandates on the spread of airborne diseases, many of which focus on different aspects of disease transmission and prevention. One such method described by Britton is by comparing the relative reduction in reproductive number (Efm ) pre- and post-intervention. We used the methods outlined in Britton to calculate the Efm, following three key dates: June 28th, 2020 the date of the Salt Lake and Summit County mask mandates, November 9th, 2020 the date of the Utah State-wide mask mandate and April 10th, 2021 the date when all mandates were lifted except in Salt Lake City. The Efm was calculated for each county in the state, 28 days before and after each mandate. Our results showed that most counties had a reduction in the growth rate of cases after the county wide and state wide mandates were put into place. There was a greater reduction in reproductive numbers after the introduction of the Salt Lake and Summit County mandates compared to the change in Efm after the statewide mandate. This could be a result of county level mask mandates already being in effect across the state at the time of the introduction of the statewide mandate, leading to a reduced reduction in cases because of the mandates already in place. When the mask mandates were lifted, the Efm rose across the state in several counties, indicating that the reproductive number grew after the mandate was lifted. By studying the interventions that were used for this pandemic, we can be better prepared for future pandemics.
Citation:
Britton, Tom. "Quantifying the preventive effect of wearing face masks." Proceedings. Mathematical, physical, and engineering sciences vol. 477,2251 (2021): 20210151. doi:10.1098/rspa.2021.0151