Bidirectional contact tracing dramatically improves COVID-19 control

Bradshaw, William J.

doi:10.1101/2020.05.06.20093369

Cited by 32 publications

(50 citation statements)

References 37 publications

(63 reference statements)

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“…Furthermore, backward tracing contributes to epidemiological understanding of high-risk settings because transmission events with a common source are more likely to be identified. While standard tracing mostly focuses on forward tracing 3 , 4 , there has been increasing interest in a possible combination of forward and backward tracing to control COVID-19 13 , 19 . Our results provide further evidence for this approach by quantifying the possible benefit of backward tracing, especially when the offspring distribution is highly variable, as is the case with SARS-CoV-2.…”

Section: Discussionmentioning

confidence: 99%

“…overdispersion), often resulting in so-called superspreading events 9 – 11 , a large proportion of infections may be linked to a small proportion of original clusters. As a result, finding and targeting originating clusters in combination with reducing onwards infection may substantially enhance the effectiveness of tracing methods 12 , 13 .…”

Section: Introductionmentioning

confidence: 99%

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Implication of backward contact tracing in the presence of overdispersed transmission in COVID-19 outbreaks

et al. 2020

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Introduction: Contact tracing has the potential to control outbreaks without the need for stringent physical distancing policies, e.g. civil lockdowns. Unlike forward contact tracing, backward contact tracing identifies the source of newly detected cases. This approach is particularly valuable when there is high individual-level variation in the number of secondary transmissions (overdispersion). Methods: By using a simple branching process model, we explored the potential of combining backward contact tracing with more conventional forward contact tracing for control of COVID-19. We estimated the typical size of clusters that can be reached by backward tracing and simulated the incremental effectiveness of combining backward tracing with conventional forward tracing. Results: Across ranges of parameter values consistent with dynamics of SARS-CoV-2, backward tracing is expected to identify a primary case generating 3-10 times more infections than average, typically increasing the proportion of subsequent cases averted by a factor of 2-3. The estimated number of cases averted by backward tracing became greater with a higher degree of overdispersion. Conclusion: Backward contact tracing can be an effective tool for outbreak control, especially in the presence of overdispersion as was observed with SARS-CoV-2.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Implication of backward contact tracing in the presence of overdispersed transmission in COVID-19 outbreaks

et al. 2020

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“…Code for configuring and running the model is publicly available at https://github.com/ willbradshaw/covid-bidirectional-tracing 32 .…”

Section: Data Availabilitymentioning

confidence: 99%

Bidirectional contact tracing could dramatically improve COVID-19 control

et al. 2021

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Contact tracing is critical to controlling COVID-19, but most protocols only “forward-trace” to notify people who were recently exposed. Using a stochastic branching-process model, we find that “bidirectional” tracing to identify infector individuals and their other infectees robustly improves outbreak control. In our model, bidirectional tracing more than doubles the reduction in effective reproduction number (Reff) achieved by forward-tracing alone, while dramatically increasing resilience to low case ascertainment and test sensitivity. The greatest gains are realised by expanding the manual tracing window from 2 to 6 days pre-symptom-onset or, alternatively, by implementing high-uptake smartphone-based exposure notification; however, to achieve the performance of the former approach, the latter requires nearly all smartphones to detect exposure events. With or without exposure notification, our results suggest that implementing bidirectional tracing could dramatically improve COVID-19 control.

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“…Both biases can be at play at the same time, and thus their effects are additive, resulting in an exceptional efficacy of backward contact tracing at identifying super-spreaders and super-spreading events. Although the effectiveness of backward tracing has been explored in the literature 8,[19][20][21][22][23][24][25] , for instance by using agent-based simulations 8,22 or branching process models 20,21,[23][24][25] , a clear connection between the effectiveness and the nature of statistical biases regarding contact network structure has not yet been established.…”

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confidence: 99%