College Openings, Mobility, and the Incidence of COVID-19 Cases

Andersen, M. S.; Bento, A. I.; Basu, A.; Marsicano, C.; Simon, K.

Most U.S. colleges have reopened campuses for in-person teaching this Fall, following rapid closures at the onset of the COVID-19 pandemic this Spring. Despite administrative efforts at mitigation and preventive measures, the large congregation of students within close quarters has caused public health concerns. In this paper, we examine college reopenings' association with changes in human mobility within campuses and in COVID-19 incidence in the counties of the campuses, over a two-week period before and after college reopenings. To estimate the daily reproduction number (Rt), we used a Bayesian framework. Using a difference-in-differences design comparing areas with a college campus, before and after reopening, to areas without a campus, we find that after college reopenings for face-to-face instruction, COVID-19 incidence in the county increased on average by a statistically significant 0.024 per thousand residents, following increases in mobility on campus. Similarly, we estimated increased transmission locally after reopening, with a rising trend in Rt. The increase in cases was larger in counties with colleges that drew students from areas with increasing incidence rates.