A cluster randomised trial of the impact of a policy of daily testing for contacts of COVID-19 cases on attendance and COVID-19 transmission in English secondary schools and colleges

Abstract

Background School-based COVID-19 contacts in England are asked to self-isolate at home. However, this has led to large numbers of missed school days. Therefore, we trialled daily testing of contacts as an alternative, to investigate if it would affect transmission in schools. Methods We performed an open-label cluster randomised controlled trial in students and staff from secondary schools and further education colleges in England (ISRCTN18100261). Schools were randomised to self-isolation of COVID-19 contacts for 10 days (control) or to voluntary daily lateral flow device (LFD) testing for school contacts with LFD-negative contacts remaining at school (intervention). Household contacts were excluded from participation. Co-primary outcomes in all students and staff were symptomatic COVID-19, adjusted for community case rates, to estimate within-school transmission (non-inferiority margin: <50% relative increase), and COVID-19-related school absence. Analyses were performed on an intention to treat (ITT) basis using quasi-Poisson regression, also estimating complier average causal effects (CACE). Secondary outcomes included participation rates, PCR results in contacts and performance characteristics of LFDs vs. PCR. Findings Of 99 control and 102 intervention schools, 76 and 86 actively participated (19-April-2021 to 27-June-2021); additional national data allowed most non-participating schools to be included in the co-primary outcomes. 2432/5763 (42.4%) intervention arm contacts participated. There were 657 symptomatic PCR-confirmed infections during 7,782,537 days-at-risk (59.1/100k/week) and 740 during 8,379,749 days-at-risk (61.8/100k/week) in the control and intervention arms respectively (ITT adjusted incidence rate ratio, aIRR=0.96 [95%CI 0.75-1.22;p=0.72]) (CACE-aIRR=0.86 [0.55-1.34]). There were 55,718 COVID-related absences during 3,092,515 person-school-days (1.8%) and 48,609 during 3,305,403 person-school-days (1.5%) in the control and intervention arms (ITT-aIRR=0.80 [95%CI 0.53-1.21;p=0.29]) (CACE-aIRR 0.61 [0.30-1.23]). 14/886(1.6%) control contacts providing an asymptomatic PCR sample tested positive compared to 44/2981(1.5%) intervention contacts (adjusted odds ratio, aOR=0.73 [95%CI 0.33-1.61;p=0.44]). Rates of symptomatic infection in contacts were 44/4665 (0.9%) and 79/5955 (1.3%), respectively (aOR=1.21 [0.82-1.79;p=0.34]). Interpretation Daily contact testing of school-based contacts was non-inferior to self-isolation for control of COVID-19 transmission. COVID-19 rates in school-based contacts in both intervention and control groups were <2%. Daily contact testing is a safe alternative to home isolation following school-based exposures.

SARS-CoV-2 testing strategies to contain school-associated transmission: model-based analysis of impact and cost of diagnostic testing, screening, and surveillance

“…We project that testing to stay results in only minor increases in transmission, even at the highest community case notification rates and with conservative assumptions about test sensitivity. Such estimates are consistent with a recent randomized controlled trial of "test to stay" programs in the United Kingdom, which were layered on top of twice-weekly screening programs (38). We further find that "test to stay" strategies have lower societal costs than quarantine-based strategies and could maintain student absences to less than 0.2% of school days.…”

Implementation of School-Based COVID-19 Testing Programs in Underserved Populations

“…Despite the potential burden of regular testing, school-based COVID-19 testing has been found to enhance mitigation efforts, detect asymptomatic cases, limit in-school spread, and maximize in-person learning days. 4,[9][10][11]20 Communicating the value of testing to stakeholders--in both educational and public health terms--is critical to generating buy-in and participation. Finding testing models that are both effective and easy to implement are key to wide scale uptake.…”

“…In the absence of COVID-19 vaccines, evidence suggests the beneficial role of testing as an added mitigation strategy for schools to facilitate in-person learning. [8][9][10][11][12] While not conclusive, implementation of COVID-19 testing in schools combined with other mitigation efforts may help to identify asymptomatic cases, reduce spread, and maximize the number of in-person learning days. [8][9][10][11][12] In the strongest study to date, Young and colleagues 10 randomized secondary schools to either require quarantining of close contacts or daily testing of close contacts if asymptomatic, with findings suggesting that transmission rates were similar between groups, but the daily testing group missed fewer days of school.…”

“…[8][9][10][11][12] While not conclusive, implementation of COVID-19 testing in schools combined with other mitigation efforts may help to identify asymptomatic cases, reduce spread, and maximize the number of in-person learning days. [8][9][10][11][12] In the strongest study to date, Young and colleagues 10 randomized secondary schools to either require quarantining of close contacts or daily testing of close contacts if asymptomatic, with findings suggesting that transmission rates were similar between groups, but the daily testing group missed fewer days of school. 10 Even with the increased availability of vaccines, school-based testing will play a critical role in detecting cases where SARS-CoV-2 escapes vaccine immunity, cases in high-risk populations, cases in regions with low vaccination rates, and cases in vaccineineligible populations until vaccines are available for all.…”

“…[8][9][10][11][12] In the strongest study to date, Young and colleagues 10 randomized secondary schools to either require quarantining of close contacts or daily testing of close contacts if asymptomatic, with findings suggesting that transmission rates were similar between groups, but the daily testing group missed fewer days of school. 10 Even with the increased availability of vaccines, school-based testing will play a critical role in detecting cases where SARS-CoV-2 escapes vaccine immunity, cases in high-risk populations, cases in regions with low vaccination rates, and cases in vaccineineligible populations until vaccines are available for all. Testing may also help school communities in areas disproportionately affected by COVID-19 as it provides an added layer of reassurance against a disease that has had devastating consequences.…”