Minimal SARS-CoV-2 classroom transmission at a large urban university experiencing repeated into campus introduction

SARS-CoV-2, the causative agent of COVID-19, has displayed person to person transmission in a variety of indoor situations. This potential for robust transmission has posed significant challenges to day-to-day activities of colleges and universities where indoor learning is a focus. Concerns about transmission in the classroom setting have been of concern for students, faculty and staff. With the simultaneous implementation of both non-pharmaceutical and pharmaceutical control measures meant to curb the spread of the disease, defining whether in-class instruction without any physical distancing is a risk for driving transmission is important. We examined the evidence for SARS-CoV-2 transmission on a large urban university campus that mandated vaccination and masking but was otherwise fully open without physical distancing during a time of ongoing transmission of SARS-CoV-2 both at the university and in the surrounding counties. Using weekly surveillance testing of all on-campus individuals and rapid contact tracing of individuals testing positive for the virus we found little evidence of in-class transmission. Of more than 140,000 in-person class events, only nine instances of potential in-class transmission were identified. When each of these events were further interrogated by whole-genome sequencing of all positive cases significant genetic distance was identified between all potential in-class transmission pairings, providing evidence that all individuals were infected outside of the classroom. These data suggest that under robust transmission abatement strategies, in-class instruction is not an appreciable source of disease transmission.