Comparing the efficiency of forward and backward contact tracing.

Area of Science:

• Epidemiology
• Mathematical Modeling
• Public Health

Background:

• Contact tracing is crucial for managing infectious disease outbreaks, particularly highlighted during the COVID-19 pandemic.
• Forward contact tracing (identifying onward spread) and backward contact tracing (identifying infection sources) are key strategies.
• Previous research suggested backward tracing and source identification were superior and more cost-efficient than case isolation.

Purpose of the Study:

• To re-evaluate the comparative effectiveness and cost-efficiency of forward versus backward contact tracing strategies.
• To investigate the influence of disease dynamics on the optimal contact tracing approach.
• To correct for potential overestimations in prior simulations of contact tracing efficacy.

Main Methods:

• Development and application of simulation models to assess contact tracing strategies.
• Comparison of forward and backward tracing under varying disease transmission parameters.
• Analysis of cost-efficiency, defined as prevented infections per isolation.

Main Results:

• The effectiveness and efficiency of contact tracing strategies are highly contextual and depend on specific disease dynamics.
• Backward contact tracing is not universally more effective than forward tracing; the optimal strategy varies.
• Previous conclusions regarding the superiority of backward tracing and its cost-efficiency were based on simulations that overestimated effectiveness.

Conclusions:

• The choice between forward and backward contact tracing should be informed by the specific characteristics of the infectious disease and the outbreak.
• Simulating disease spread and mitigation measures concurrently, rather than sequentially, provides more accurate assessments.
• Contact tracing efficacy is not solely dependent on identifying infection sources but is influenced by broader epidemiological factors.