Efficacy of COVID-19 Public Health Measures in Philadelphia, New York City, Baltimore, and Chicago.

INTRODUCTION: From the early days of the pandemic, US cities have implemented a variety of public health measures to reduce the spread of COVID-19. This study investigates which policies were most effective in reducing cases of COVID-19 in four major cities: Philadelphia, New York City, Baltimore, and Chicago. METHODS: Through a cross-comparative analysis, we developed a timeline that tracked the implementation of a range of public health measures along with changes in COVID-19 cases, hospitalizations, and deaths. Data were collected from publicly available government sites and from press releases. RESULTS: The results from the stay-at-home orders illustrate the delayed impact it has in reducing COVID-19 cases and hospitalizations. The mask mandate led to the immediate and sustained reduction in cases across all four cities. During the spike of COVID-19 in the Fall of 2020, restrictions on indoor dining contributed significantly to reducing COVID-19 cases. DISCUSSION: Of all the measures that were examined, the implementation of mask mandates was most closely associated with a decline in COVID-19 cases, hospitalizations, and deaths across all four cities. Restrictions on indoor dining were also associated with a reduction in COVID-19 cases. Future studies should further investigate the adherence to different policies to better understand their impacts.