Pilot Investigation of SARS-CoV-2 Secondary Transmission in Kindergarten Through Grade 12 Schools Implementing Mitigation Strategies — St. Louis County and City of Springfield, Missouri, December 2020

Dawson, Patrick; Worrell, Mary Claire; Malone, Sara; Tinker, Sarah C.; Fritz, Stephanie; Maricque, Brett; Junaidi, Sadaf; Purnell, Gemille; Lai, Albert M.; Neidich, Julie A.; Lee, Justin S.; Orscheln, Rachel C.; Charney, Rachel; Rebmann, Terri; Mooney, Jon; Yoon, Nancy; Petit, Machelle; Schmidt, Spring; Grabeel, Jean; Neill, Lee Ann; Barrios, Lisa C.; Vallabhaneni, Snigdha; Williams, Randall W.; Goddard, Clay; Newland, Jason G.; Neatherlin, John C.; Salzer, Johanna S.; Tong, Suxiang; Tao, Ying; Emery, Brian; Zhang, Jing; Chen, Min-hsin; Kim, Gimin; Bankamp, Bettina

Many kindergarten through grade 12 (K-12) schools offering in-person learning have adopted strategies to limit the spread of SARS-CoV-2, the virus that causes COVID-19 (1). These measures include mandating use of face masks, physical distancing in classrooms, increasing ventilation with outdoor air, identification of close contacts,* and following CDC isolation and quarantine guidance†(2). A 2-week pilot investigation was conducted to investigate occurrences of SARS-CoV-2 secondary transmission in K-12 schools in the city of Springfield, Missouri, and in St. Louis County, Missouri, during December 7-18, 2020. Schools in both locations implemented COVID-19 mitigation strategies; however, Springfield implemented a modified quarantine policy permitting student close contacts aged ≤18 years who had school-associated contact with a person with COVID-19 and met masking requirements during their exposure to continue in-person learning.§ Participating students, teachers, and staff members with COVID-19 (37) from 22 schools and their school-based close contacts (contacts) (156) were interviewed, and contacts were offered SARS-CoV-2 testing. Among 102 school-based contacts who received testing, two (2%) had positive test results indicating probable school-based SARS-CoV-2 secondary transmission. Both contacts were in Springfield and did not meet criteria to participate in the modified quarantine. In Springfield, 42 student contacts were permitted to continue in-person learning under the modified quarantine; among the 30 who were interviewed, 21 were tested, and none received a positive test result. Despite high community transmission, SARS-CoV-2 transmission in schools implementing COVID-19 mitigation strategies was lower than that in the community. Until additional data are available, K-12 schools should continue implementing CDC-recommended mitigation measures (2) and follow CDC isolation and quarantine guidance to minimize secondary transmission in schools offering in-person learning.