Citation
Grantz, Kyra H.; Lee, Elizabeth C.; D'Agostino McGowan, Lucy; Lee, Kyu H.; Metcalf, Jessica; Gurley, Emily S.; & Lessler, Justin (2021). Maximizing and Evaluating the Impact of Test-Trace-Isolate Programs: A Modeling Study. PLOS Medicine, 18(4), e1003585. PMCID: PMC8121292Abstract
BACKGROUND: Test-trace-isolate programs are an essential part of coronavirus disease 2019 (COVID-19) control that offer a more targeted approach than many other nonpharmaceutical interventions. Effective use of such programs requires methods to estimate their current and anticipated impact.METHODS AND FINDINGS: We present a mathematical modeling framework to evaluate the expected reductions in the reproductive number, R, from test-trace-isolate programs. This framework is implemented in a publicly available R package and an online application. We evaluated the effects of completeness in case detection and contact tracing and speed of isolation and quarantine using parameters consistent with COVID-19 transmission (R0: 2.5, generation time: 6.5 days). We show that R is most sensitive to changes in the proportion of cases detected in almost all scenarios, and other metrics have a reduced impact when case detection levels are low (<30%). Although test-trace-isolate programs can contribute substantially to reducing R, exceptional performance across all metrics is needed to bring R below one through test-trace-isolate alone, highlighting the need for comprehensive control strategies. Results from this model also indicate that metrics used to evaluate performance of test-trace-isolate, such as the proportion of identified infections among traced contacts, may be misleading. While estimates of the impact of test-trace-isolate are sensitive to assumptions about COVID-19 natural history and adherence to isolation and quarantine, our qualitative findings are robust across numerous sensitivity analyses.
CONCLUSIONS: Effective test-trace-isolate programs first need to be strong in the "test" component, as case detection underlies all other program activities. Even moderately effective test-trace-isolate programs are an important tool for controlling the COVID-19 pandemic and can alleviate the need for more restrictive social distancing measures.
URL
http://dx.doi.org/10.1371/journal.pmed.1003585Reference Type
Journal ArticleYear Published
2021Journal Title
PLOS MedicineAuthor(s)
Grantz, Kyra H.Lee, Elizabeth C.
D'Agostino McGowan, Lucy
Lee, Kyu H.
Metcalf, Jessica
Gurley, Emily S.
Lessler, Justin