Modeling Contact Tracing Strategies for COVID-19 in the Context of Relaxed Physical Distancing Measures

Abstract

This mathematical modeling study examines the potential for contract tracing to reduce the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the context of reduced physical distancing under different assumptions for case detection, tracing, and quarantine efficacy.

Figure 1.. Model Structure and Parameters

Parameter definitions: a is the fraction of infections that are asymptomatic; k, the fraction of infections that are detected; r, the number of secondary infections from each infection; and p, the fraction of cases that are successfully contact traced. For parameters indexed by subscripts: T is contact traced; N, not contact traced; S, symptomatic; A, asymptomatic; D, detected; and U, undetected. Parameter values are reported in the eAppendix in the Supplement.

Figure 2.. Reductions in the Effective Reproductive Number (R_t) Associated With Contact Tracing Strategies Under Varying Assumptions Regarding Key Program Features

Outcomes measured as percentage reductions in R_t in the contact tracing scenario relative to R_t without contact tracing. Isolation and quarantine efficacy refers to the level of reduction in transmission rates from traced, undetected contacts. Modeled estimates of relative reductions do not depend on current levels of R_t.