Modelling the impact of presemester testing on COVID-19 outbreaks in university campuses

OBJECTIVES: Universities are exploring strategies to mitigate the spread of COVID-19 prior to reopening their campuses. National guidelines do not currently recommend testing students prior to campus arrival. However, the impact of presemester testing has not been studied. DESIGN: Dynamic SARS-CoV-2 transmission models are used to explore the effects of three presemester testing interventions. INTERVENTIONS: Testing of students 0, 1 and 2 times prior to campus arrival. PRIMARY OUTCOMES: Number of active infections and time until isolation bed capacity is reached. SETTING: We set on-campus and off-campus populations to 7500 and 17 500 students, respectively. We assumed 2% prevalence of active cases at the semester start, and that one-third of infected students will be detected and isolated throughout the semester. Isolation bed capacity was set at 500. We varied disease transmission rates (R(0)=1.5, 2, 3, 4) to represent the effectiveness of mitigation strategies throughout the semester. RESULTS: Without presemester screening, peak number of active infections ranged from 4114 under effective mitigation strategies (R(0)=1.5) to 10 481 under ineffective mitigation strategies (R(0)=4), and exhausted isolation bed capacity within 10 (R(0)=4) to 25 days (R(0)=1.5). Mandating at least one test prior to campus arrival delayed the timing and reduced the size of the peak, while delaying the time until isolation bed capacity was reached. Testing twice in conjunction with effective mitigation strategies (R(0)=1.5) was the only scenario that did not exhaust isolation bed capacity during the semester. CONCLUSIONS: Presemester screening is necessary to avert early and large surges of active COVID-19 infections. Therefore, we recommend testing within 1 week prior to and on campus return. While this strategy is sufficient for delaying the timing of the peak outbreak, presemester testing would need to be implemented in conjunction with effective mitigation strategies to significantly reduce outbreak size and preserve isolation bed capacity.