COVID-19 Testing and Case Rates and Social Contact Among Residential College Students in Connecticut During the 2020-2021 Academic Year

Key Points Question What is the association between COVID-19 testing and case rates on residential college campuses? Findings In this cohort study of 18 Connecticut colleges and universities, infrequent COVID-19 testing of residential students was not associated with decreased transmission, whereas testing of residential students twice per week was associated with decreased transmission during the 2020-2021 academic year. Meaning Findings suggest that twice-weekly COVID-19 testing of residential students may serve as an effective infection mitigation strategy at colleges and universities.

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Statistical methodology
To evaluate the association between the average residential case rate in institution in semester with the average test rate in that institution, adjusting for the average case rate in the surrounding town, we fit a linear model is an independent error term for institution in semester . The estimated coefficients and 95% confidence intervals are shown in eTable 2.
To evaluate the change in close interpersonal contact when residential students were brought back to campus, we fit the following linear regression model for institution in week : where the coefficient corresponds to the interaction of the indicator that students are in residence and semester, and is an independent error term for institution in week . The estimated coefficients and 95% confidence intervals are given in the main text.
To visualize the weekly change in average contact following arrival of residential students on campus, we fit the following model ( ) = ( ) ( ) + where is measured in weeks relative to arrival of students on campus. eFigure 4 shows estimated weekly coefficients and 95% confidence intervals for both semesters.
To evaluate the association between the residential case rate in institution in week with the weekly test rate in that institution, while adjusting for the case rate in the surrounding town, we fit a linear model where the sum is over discretized weekly residential testing rate with bins (tests per residential student per week): To evaluate the association between case rates in towns where institutions are located and case rates in those institutions, we fit a linear model ( ) = + ( ) + where the coefficient corresponds to semester and is an independent error term for institution in semester . Estimated coefficients are shown in eTable 3.

Details of university plans and policies
eTable 1 shows summary information on COVID-19 residential student testing policies for 18 Connecticut colleges and universities according to public documents and plans submitted to the Connecticut Department of Public Health (CT DPH). We examined four institutions that grant baccalaureate degrees and eleven that also offer masters or doctoral degrees. The number of residential students in the fall ranged from 235 (Albertus Magnus College) to 4,603 (University of Connecticut). Most institutions had fewer residential students in the spring semester. In the fall, CT DPH recommended that students test negative within 14 days of returning to campus. Ten institutions adopted this policy, while seven required a negative test within 7 days of move-in. The University of Connecticut did not require pre-arrival testing but tested students on move-in day; three other universities also tested students upon move-in. Eleven institutions outlined plans to comply with an initial 14-day quarantine for students coming from "hot spot" areas as mandated by Executive Order 7III 1,2 . Five required all students to quarantine regardless of origin, and two did not have available data on arrival quarantine policies. Thirteen institutions planned for to test 5-10% of residential students each week, the level recommended by CT DPH, while Quinnipiac University stated it would test 15% of students per week. Connecticut College, Trinity College, Wesleyan University, and Yale University stated they would test residential students at least once per week. Twelve institutions implemented a daily health check throughout the semester, while three had a health check for the first 7 days as recommended by CT DPH. Two institutions didn't have include information on a daily health check in their reopening plans.
CT DPH issued updated guidance for spring 2021 in early January, following several college outbreaks during the fall and increasing statewide incidence 3 . Recommendations for residential students included entry testing within 7 days before move-in and on move-in day, a 7-14 day quarantine period, and continued weekly testing through the end of February. Twelve institutions required a test within 7 or fewer days prior to move-in with 5 giving larger windows (i.e., 10 or 14 days) for pre-arrival tests. No data on testing, quarantine policy, or daily health checks was available from the University of Saint Joseph for the spring semester. Eleven school explicitly stated that students were tested on move-in day, while three other schools specified students would be tested within 2-5 days following move-in (Fairfield University), within 6-10 days following move-in (University of Bridgeport) and within 9 days following move-in (University of New Haven), respectively. Though no other schools explicitly specified testing students upon arrival, most had plans stating they were conducting weekly testing of residential students at the beginning of the semester; therefore, it is feasible this weekly testing began the day of move-in. Fourteen institutions reported implementing a quarantine of 7 days or longer for residential students, in line with CT DPH recommendations. Four had no available data on initial quarantine. Sixteen institutions planned to test students at least weekly through the end of February, as recommended by CT DPH; as in the fall semester, Connecticut College, Trinity College, Wesleyan University, and Yale University stated plans to test students more than once per week. During the spring semester, CT DPH extended its weekly testing recommendations through the end of the semester 4,5 ; this guidance is not reflected in institutions' reopening plans which were submitted prior to the start of the semester. Twelve institutions adopted a daily health check throughout the semester, while three implemented this measure only for the first 7 days following move-in and three did not include information on this in their reopening plans.

Cases as a function of contact
In both the fall and spring semesters, institutions with higher contact rates had higher case rates (eFigure 6). In the fall semester, most colleges were conducting low levels of testing (less than half of residential students per week). The four institutions with the highest testing rates (Connecticut College, Trinity College, Wesleyan University, and Yale University) had low contact rates and low case rates. Case rates were higher in the spring semester, despite higher testing rates and similar or lower testing rates. As in the fall semester, the four institutions testing students twice per week had the lowest contact rates and case rates.
Percent of residential student cases detected through institution screening program eFigure 7 presents data on the frequency of residential student testing and the proportion of cases detected through each institution's screening program (compared with the proportion self-reported by students). In the fall, Yale University and the four state universities didn't report data on self-reported cases. Of the institutions that reported, four institutions detected nearly all cases through their residential testing program (Connecticut College, Mitchell College, Trinity College, and Wesleyan College); of those institutions, three tested their students more than once per week. The remaining institutions detected at least 50% of residential student cases through the testing program, with the exception of Albertus Magnus College. In the spring, increased testing frequency did not lead to improved proportion of cases detected within the testing program. Three of the four institutions detecting almost every case through the testing program (Connecticut College, Wesleyan University, Western Connecticut State University, and Yale University) tested students more than once per week. It is unclear how practices on recording self-reported tests varied between institutions.