ABSTRACT
Background. Case and contact investigation is a mitigation strategy to understand transmission of diseases. The goal of this study is to assess COVID-19 transmission in schools that employ contact tracing. Methods. Five middle and high schools provided a list of ongoing student and staff cases and their school contacts for the 2021-22 school year. Cases were eligible for interview if they had a known positive test or were a 'presumed positive' by a practitioner. Contacts were eligible if they were identified as a close contact to a case within their school. Contacts who later became a case were eligible for a separate case interview. Trained interviewers contacted eligible individuals to offer COVID-19 resources and determine interests in participating in the study. Interested cases and contacts underwent a semi-structured interview with standardized questions. Results. From 5/2021-4/2022, 360 cases (45% during Omicron surge) and their 412 contacts were identified (Fig 1).Among the 111 cases interviewed, 75% were students, half were in grades 6-8 (Fig 2). 61% of the cases were vaccinated with their primary series. 92% were symptomatic and fatigue, cough, and headaches were the most common symptoms. Transmission from school occurred in 29% (Fig 3) and most commonly occurred in the classroom. Among the 68 contacts interviewed, 96% were students. The two most reported activities contacts participated in were band (n=9) and sports (n=22), 10 from playing basketball. Three contacts reported exposure to COVID-19 within the household and five contacts reported exposure outside the home or school. Conclusion. Case and contact investigation can be a valuable tool to assess COVID-19 transmission in schools. Almost one-third of cases reported school exposures, a greater school transmission rate than previous reported likely do to the increased transmissibility of Omicron. Assessing transmission events with this strategy alone may be limited by its reliance on self-reports. Case investigations can help schools identify potential areas to improve in limiting school-based COVID-19 transmission.