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Return to University Campuses Associated with 9% Increase in New COVID-19 Case Rate

Our take —

This study, available as a preprint and thus not yet peer reviewed, demonstrates that there was a 9% increase in the number of new cases in college counties compared with non-college counties during the period when many colleges and universities reopened (June to September, 2020). However, these results should be interpreted with caution because some of these differences in college and non-college counties could be explained by: 1) a greater influx of people at the time of reopening; and/or 2) an increase in testing as part of university reopening policies, rather than true increases in risk. Further research will be needed to understand the impact of college reopenings on community transmission, if any.

Study design


Study population and setting

Publicly available data from the New York Times COVID-19 database, the US Census Bureau, and the American Community Survey were used to describe differences in the number of COVID-19 cases in college counties (counties where 10% of more of the population is enrolled in college) compared with non-college counties after the initial return to college. Case counts were observed between June 14 and September 6, 2020 at the county level, and there were a total of 3118 county-day observations. The primary outcome of interest was defined as the number of new cases in the three weeks prior to September 6divided by the total number of cases in the twelve weeks prior to September 6, and this was referred to as the “new case rate.” This is a measure of the distribution of cases over the prior twelve weeks, with equal distribution equating to about 0.25 (25%). A “surge” was defined as a proportion greater than 0.25 and a “tapering off” was a proportion less than 0.25.

Summary of Main Findings

Compared with non-college counties, college counties experience a 9% greater increase in the COVID-19 case rate during the return to campus. There were substantial regional differences, ranging from 3.4% in the Pacific Division to 18.9% in the West North Central Division. The median new case rate was greater than 25% for college counties in all divisions except for the Pacific and Mountain Divisions, indicating a “surge” in cases the last three weeks. The highest new case rate was observed in the West North Central Division at 54.6% of all cases in the last week experienced in the last three weeks.

Study Strengths

This study uses aggregate data to quantify differences between college and non-college counties when reopening. The use of the “new case rate” as the outcome allows for comparison across counties and the ability to establish whether or not there was a surge in new cases.


When comparing college counties to non-college counties, some of the increase in new cases in college counties could in part be due to an influx of people returning to college rather than a greater level of transmission. Additionally, there is no discussion of changes in testing patterns at the time of return to campus. Many colleges and universities have been implementing large-scale weekly or even bi-weekly mandatory testing of all their students, faculty, and staff. Part of the observed difference between college and non-college counties could be due to increases in testing.

Value added

This study quantifies an increased number of cases reported from counties where colleges reopened compared to other communities without colleges.

This review was posted on: 7 December 2020