key: cord-0931185-89328snx
authors: 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
title: Screening Students and Staff for Asymptomatic COVID-19 in Chicago Schools
date: 2021-08-18
journal: J Pediatr
DOI: 10.1016/j.jpeds.2021.08.017
sha: 4bdeeef1affe6ad347e98340d660289c32d8e87a
doc_id: 931185
cord_uid: 89328snx

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.

In response to the coronavirus disease 2019 (COVID- 19) pandemic, most schools in the U.S. transitioned to remote learning in March of 2020, and many had not returned to an inperson educational setting prior to the end of 2020-2021 school year. Although children with COVID-19 often have relatively mild or asymptomatic illness 1, 2 , there is concern that children could be vectors for severe acute respiratory syndrome coronavirus-2 (SARS- transmission to others in the school setting, even in the presence of risk mitigation strategies such as masking, physical distancing, testing and isolation, and quarantine of those exposed.

Observational studies have indicated a few instances of suspected transmission in school settings when SARS-CoV-2-positive students have been identified. These cases are often linked to breaches in established COVID-19 risk mitigation practices or linked to activities outside of the school setting 3, 4 . Due to differences in COVID-19 prevalence across communities, risk mitigation practices in schools, and in the design of prior studies (eg, efforts to identify both symptomatic and asymptomatic COVID-19 in students), generalizing previous research findings has been challenging. Thus, there is an unmet need to understand the risk of SARS-CoV-2 transmission in schools, particularly among asymptomatic children and in communities highly impacted by As schools across the U.S. evaluate plans for safe in-person learning, there is a need to identify the necessary measures to mitigate SARS-CoV-2 school transmission in a cost-effective and evidence-based manner. The objectives of this prospective observational study were to understand the prevalence of asymptomatic COVID-19 among students and staff in K-8 schools in high-risk Chicago communities, and to assess possible cases of SARS-CoV-2 transmission within the classroom or student households. screening testing was performed at eleven K-8 schools between January and March of 2021 (i.e., between winter and spring breaks). High-risk zip codes were defined by longitudinally sustained higher than average case counts per resident and used to inform choice of schools for screening as described below. COVID-19 incidence rates in these zip codes were higher than citywide rates throughout most of the pandemic, though during the time of school visits, case rates in these high-risk zip codes reached a nadir and were equivalent to COVID-19 incidence observed citywide 5 . During the study period, weekly COVID-19 cases in the zip codes of the schools and citywide were all greater than 50/100,000 population, and would be classified as substantial or high levels of community transmission 6 (Figure 2 [available at www.jpeds.com]). Descriptive statistics were used to analyse data; proportions and medians were measured, and figures and tables were created using Microsoft Excel v16.49 and R v4.0.2.

All schools were part of the Archdiocese of Chicago, a large private school system of 160 K-8 schools in Chicago and surrounding suburbs that offered parents the choice of in-person or remote learning starting in the fall of 2020. Among the 84 schools in Chicago city limits, 36 are in areas with low or very low child opportunity index. 7 All schools visited during this study were within 8 high-risk Chicago zip codes based on relative COVID-19 incidence and/or low or very low child opportunity index 7 (Figure 1 ). Eligible schools in these high-risk communities were additionally chosen for participation based on school size, percent of in-person enrollment, and agreement to participation by school administrators at each eligible school. Although the target study population to whom screening testing was offered was all in-person students and staff at each school, remote students were also offered testing. Each school was visited one time during the study period to conduct testing; this was the only study test for participants.

Testing was only performed for those providing informed consent. In addition to the research-related screening testing, the Lurie Children's Mobile Health Unit was made available to visit any Archdiocese school for clinical COVID-19 testing at the discretion of the school system and/or Chicago Department of Health if there was concern for extensive COVID-19 exposure events or suspected COVID-19 outbreak.

All schools abided by the same COVID-19 mitigation measures that were implemented throughout the school system. This included: grouping students and teachers in self-contained cohorts to minimize cross-cohort exposure; symptom screening of students and household contacts prior to arrival at school; student temperature screening upon arrival to school; universal masking for all students and staff; and physical distancing of 6 feet between students and between students and staff. Reports from principals at each school, which were confirmed by study team observations on testing days, was that COVID-19 risk mitigation was strictly followed. If a student or their household member tested positive for COVID-19 or developed symptoms of COVID-19 prior to testing, families were required to report this to the school and quarantine per CDC guidelines or until verification of a negative COVID-19 test result 8 . If a member of a cohort tested positive for COVID-19, all members of that cohort were considered exposed, and the cohort transitioned to remote learning while cohort students and staff were under quarantine 9 .

For screening testing, oropharyngeal swabs were collected at each school from study participants and stored in universal transport medium. Specimens were heat inactivated and viral Park, IL). Notably, to improve sensitivity of this initial assay, a high Ct cut-off for confirmatory testing was used. Qualitatively, this assay was previously validated in comparison with a clinical assay using a positivity threshold (Ct value = 35) averaged across two technical replicates, which equates to 1478 genomes per mL of viral transport media. We determined the limit of detection of this assay as Ct value = 37, which equates to 370 genome equivalents per mL of viral transport media. Thus, follow-up confirmatory testing of all samples with a Ct value < 40 on at least one of two technical replicates of this initial assay ensured exceeding low likelihood of false negative results. Positive samples from the CLIA certified laboratory assay were reported to participants, schools, and the Chicago Department of Public Health. For clinical testing related to extensive COVID-19 exposure events or suspected COVID-19 outbreak, nasopharyngeal swabs were collected and processed using the Abbott RealTime™ SARS-CoV-2 RT-PCR assay.

Prior to testing, personal or household history of COVID-19 test results, symptoms, and exposures were collected by phone and/or electronic survey. Questions regarding personal COVID-19 vaccination history were added for adult participants in February 2021. Study data were collected and managed using REDCap electronic data capture tools hosted at Northwestern University 10, 11 . Following diagnosis of COVID-19 by CLIA-certified laboratory testing and/or the development of symptoms consistent with COVID-19 by study participants, symptoms and J o u r n a l P r e -p r o o f weeks following the positive test date. Students and staff within the cohort of SARS-CoV-2positive participants transitioned to remote learning and were recommended to remain quarantined at home per school protocols. Students and staff within the affected cohort, and household contacts of SARS-CoV-2-positive participants were referred for COVID-19 testing.

Principals were contacted two weeks after positive test collection to ascertain reported confirmed or suspected COVID-19 illness in students, staff, and families of those in both the quarantined and unaffected cohorts.

Eleven K-8 schools were visited for SARS-CoV-2 screening testing over a 9-week period between January and March 2021. In total, 468 participants were tested: 346 students and 122 staff members. The overall and median proportion of in-person students tested among all schools was 20%, ranging from 7-52% by school. Remote students represented 4.6% of the student study participants. Note that although all schools were located in high-risk zip codes for COVID-19, some participants resided in a neighboring zip code, though these generally had similar COVID-19 incidence (Figure 3) . Some participants also resided in neighboring non-Chicago zip codes, for which community COVID-19 incidence data was unavailable ( Table 2) .

Study participants were contacted to evaluate for signs of household transmission within 2 weeks of screening testing, and school adminstrators were contacted to identify new COVID-19 cases reported among non-participants. In each of the schools visited, cohorts of participating students with a positive test were quarantined and transitioned to remote learning for the recommended duration of quarantine. One student from School 2 reported one day of mild headache and abdominal pain 6 days after the positive test. All other students who tested positive remained asymptomatic. In the households of these positive individuals, one household member of a student who tested positive at School 6 became symptomatic and tested positive for COVID-19 the day following the student's test ( Table 2) . At all schools, including School 1, no COVID-19 infections were reported in the two weeks following the study visit date, neither in the affected nor the non-affected cohorts.

Study participants were also contacted regarding personal and household history of COVID-19 testing and symptoms present prior to screening testing. In School 1, of the 17 participants who tested positive, 7 (41.1%) reported personal or household history of a positive J o u r n a l P r e -p r o o f COVID-19 diagnosis or symptoms in the previous 4 months. Of the 18 participants who tested negative at School 1 and were able to be contacted, 9 (50%) reported prior symptoms or positive tests in themselves or household members in the previous 4 months. In Schools 2-11, few participants or household members (2.5%) had any personal or household contacts with symptoms of COVID-19 within 30 days of the testing date. There were reported prior positive tests in 14.6% of participants and 25% of household members, however, most (90%) of these tests were greater than 3 months prior to testing date with our study.

Two additional schools were visited for COVID-19 testing for specific outbreak investigations in February 2021, separate from screening testing initiatives. In the first of these schools, 73 of 88 in-person students and staff were tested approximately 1 week following an exposure event where 40 students and staff members were exposed to a positive staff member in a large group, in-school activity where all attendents were in the same room while masked, though with incomplete compliance with physical distancing, for approximately one hour. The positive staff member became symptomatic within 24 hours following the event. All 73 exposed individuals tested negative. At the second school, 18 individuals in the school across 6 cohorts had tested positive over a 2-week period. These cohorts were quarantined, and 193 individuals from these cohorts were offered testing. Of the 81 tested, there were 80 negative results and 1 indeterminant result due to amplification failure. Getting children back to in-person classes safely is an important goal. The closure of inperson learning not only had drastic impacts on education, but also highlighted the importance of in-person learning for psychosocial and interpersonal development in school age children.

Access to mental health and counseling services, school food programs, and other resources previously available to students in school was limited for children during the pandemic [13] [14] [15] [16] .

These negative effects are most likely to be acutely felt in communities with known socioeconomic disparities, which have also been disproportionately impacted by COVID-19 17 .

J o u r n a l P r e -p r o o f subsequent secondary infections is one potential risk mitigation strategy when planning safe return to the classroom. However, our data add to the growing evidence that risk mitigation strategies including masking and physical distancing, and staying home when ill, can be sufficient to prevent secondary transmission of SARS-CoV-2 in a school setting 18, 19 . In addition, with recent declines in COVID-19 in all age groups across the US with vaccination of adults and adolescents, the public health and economic value of screening testing may also decline further and continue to decline when vaccine is expanded to young children. The potential harms of widespread school screening testing programs should also be considered and include the possibility of identifying false positive tests and/or positives without clinical or public health significance, leading to unnecessary school absence, quarantine of household members, and anxiety among families and schools. The cost of screening testing in schools and need for school personnel to perform tests and report results are also important considerations. Estimations of cost for once-weekly testing of all K-12 students and twice-weekly testing of school staff in the United States amount to up to $8.5 billion dollars per month 20 . Without providing a clear benefit in the context of comprehensive school risk mitigation strategies, directing these funds to other pediatric pandemic-related resources, such as mental health services and academic enrichment, may benefit children more than school COVID-19 testing programs.

Our study does have several limitations. The proportion of students participating at each school averaged 20%. Although this makes it possible that transmission events were missed, we would have anticipated that some new clinical infections in other students would have been reported in that case. Some reasons reported to the study team from school leadership for hesitation towards testing included concerns of missing school or work during the required J o u r n a l P r e -p r o o f quarantine period given a positive result, concern over discomfort of the swab test itself, and mandatory sharing of positive test results with the local health department. Additionally, as school staff became eligible for the COVID-19 vaccine during the study period, we received feedback from vaccinated staff members indicating that they did not perceive COVID-19 testing to be beneficial. Though all exposed contacts both from school cohorts and households of the positive participants were referred for COVID-19 testing, few followed up for testing at our hospital. As part of this study, we had intended to perform whole genome sequencing on positive samples to more rigorously evaluate potential school transmission by assessing genetic relatedness of viral samples. However, all positive samples except three had insufficiently low Ct values to permit whole genome sequencing, mandating a reliance on more traditional epidemiological methods such as contact tracing. Furthermore, although we intended to perform testing during periods of higher COVID-19 community activity, COVID-19 incidence decreased significantly during the study planning period. Additionally, potentially more transmissible COVID-19 variants of concern were not identified through our hospital surveillance activities until after the study was completed; Alpha and Gamma variants were first identified to be increasing in Chicago children in March 2021; and Delta variant was first identified in Chicago children in June 2021 (unpublished data). It is likely that risk of transmission in a school setting is higher when overall community burden of disease is concordantly higher and/or there is a higher prevalence of more transmissible variants.

In summary, with several risk mitigation strategies in place, we identified limited evidence of SARS-CoV-2 transmission in K-8 schools in high-risk communities through our prospective observational study of COVID-19 school screening testing. Our findings support the safety of in-person learning and question the benefit of screening testing in schools that utilize J o u r n a l P r e -p r o o f funds could be spent on other resources rather than on random testing of asymptomatic students.

Testing could be potentially useful in identifying the relative impact of individual risk mitigation strategies to guide iterative de-escalation of these strategies, especially as vaccination increases.

Additional research is needed to understand the impact of screening testing in high schools, the potential benefit of testing if risk mitigation strategies are relaxed, and the potential benefit in communities during periods of high community COVID-19 incidence and/or prevalence of variants of concern.

J o u r n a l P r e -p r o o f where schools were located, and solid line represents overall citywide COVID-19 incidence.

Background colors correspond to levels of community transmission per CDC stratification. 6 .Shaded area represents time period fromStudy period from January-March 2021when school testing visits occurred is marked by gray box. 

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None * Samples with a Ct value less than the internal control of the assay. These are the only samples with an approximate upper airway viral load greater than 1000 amplicon copies per ml.