Screening Students and Staff for Asymptomatic COVID-19 in Chicago Schools

Edward, Priya R.; Reyna, Megan E.; Daly, Mary Kate; Hultquist, Judd F.; Muller, William J.; Ozer, Egon A.; Lorenzo-Redondo, Ramon; Seed, Patrick C.; Simons, Lacy M.; Sheehan, Karen; Staples, Jacinta; Kociolek, Larry

OBJECTIVES: To assess rates of asymptomatic SARS-CoV-2 positivity in K-8 schools with risk mititgation procedures in place, and to evaluate SARS-CoV-2 transmission in school and household contacts of these positive individuals. STUDY DESIGN: In this prospective observational study, screening testing for SARS-CoV-2 was performed by oropharyngeal swabbing and PCR in students and staff at K-8 private schools in high-risk Chicago zip codes. New COVID-19 diagnoses or symptoms among participants, household contacts, and non-participants in each school were queried. RESULTS: Among 11 K-8 private schools across 8 Chicago zip codes, 468 participants (346 students, 122 staff members) underwent screening testing. At the first school, 17 participants (36%) tested positive, but epidemiologic investigation suggested against in-school transmission. Only 5 participants in the subsequent 10 schools tested positive for an overall 4.7% positivity rate (1.2% excluding School 1). All but one positive test among in-person students had high PCR cycle threshold values, suggesting very low SARS-CoV-2 viral loads. In all schools, no additional students, staff, or household contacts reported new diagnoses or symptoms of COVID-19 during the two weeks following screening testing. CONCLUSIONS: We identified infrequent asymptomatic COVID-19 in schools in high-risk Chicago communities and did not identify transmission among school staff, students, or their household contacts. These data suggest that COVID-19 mitigation procedures, including masking and physical distancing, are effective in preventing transmission of COVID-19 in schools. These results may inform future strategies for screening testing in K-8 schools.