Examination of SARS-CoV-2 In-Class Transmission at a Large Urban University With Public Health Mandates Using Epidemiological and Genomic Methodology

Abstract

Importance: 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 and concerns for day-to-day activities of colleges and universities where indoor learning is a focus for students, faculty, and staff.

Objective: To assess whether in-class instruction without any physical distancing, but with other public health mitigation strategies, is a risk for driving SARS-CoV-2 transmission.

Design, setting, and participants: This cohort study examined the evidence for SARS-CoV-2 transmission on a large urban US university campus using contact tracing, class attendance, and whole genome sequencing during the 2021 fall semester. Eligible participants were on-campus and off-campus individuals involved in campus activities. Data were analyzed between September and December 2021.

Exposures: Participation in class and work activities on a campus with mandated vaccination and indoor masking but that 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.

Main outcomes and measures: Likelihood of in-class infection was assessed by measuring the genetic distance between all potential in-class transmission pairings using polymerase chain reaction testing.

Results: More than 600 000 polymerase chain reaction tests were conducted throughout the semester, with 896 tests (0.1%) showing detectable SARS-CoV-2; there were over 850 cases of SARS-CoV-2 infection identified through weekly surveillance testing of all students and faculty on campus during the fall 2021 semester. The rolling mean average of positive tests ranged between 4 and 27 daily cases. Of more than 140 000 in-person class events and a total student population of 33 000 between graduate and undergraduate students, only 9 instances of potential in-class transmission were identified, accounting for 0.0045% of all classroom meetings.

Conclusions and relevance: In this cohort study, the data suggested that under robust transmission abatement strategies, in-class instruction was not an appreciable source of disease transmission.

Figure 1.. SARS-CoV-2 Positive Test Rates at Boston University (BU) and in Massachusetts Over the Study Period

In the Massachusetts data in panel D, less than 1% non-Delta sequences were observed out of approximately 48 000 total cases (37 unassigned, 13 Omicron, 7 Mu, 5 Gamma, and 106 non–variant of concern).

Figure 2.. Identified Potential Incidents of Classroom Transmission

Listed dates indicate approximate collection date for the first case in each cluster. See Table for more information on each cluster.

Figure 3.. Sequence Comparison of SARS-CoV-2 Genomes From Potential In-Class Transmission Events

Nucleotide changes were identified at the consensus level (≥50%) are highlighted according to the nucleotide difference identified in the second genome. Low-coverage ends were masked for comparison.