Contrasting the impact and cost-effectiveness of successive intervention strategies in response to Ebola in the Democratic Republic of the Congo, 2018-2020.

Introduction: The 10th outbreak of Ebola Virus Disease (EVD) in the Democratic Republic of the Congo (DRC) in 2018-2020 was the largest in DRC's history and the second largest worldwide. Different strategic response plans (SRPs) were implemented, and the outbreak was eventually stopped after a large scale-up of operations with the SRP 4, which benefited from all public health measures deployed during SRPs 1-3, upon which it developed a more holistic approach including community engagement, logistics and security.

Methods: We used modelling to characterise EVD transmission and assess the epidemiological impact of the two main response strategies (SRPs 1-3 vs SRP 4). We simulated potential future epidemics with different intervention scenarios, combined with a costing model to evaluate the incremental cost-effectiveness of different strategies.

Results: We estimated a mean effective reproduction number R of 1.19 (credible interval (95% CrI) = (1.13 ; 1.25)). The spatial spread was moderate with an average 4.4% (95% CrI = (3.5%; 5.4%)) of transmissions moving to different health zones. The scale-up of operations in SRP 4 coincided with a threefold reduction in transmission, and 30% faster control of EVD waves. In simulations, SRP 4 appears cost-saving, although most simulated outbreaks remain small even with SRPs 1-3.

Conclusion: Most EVD outbreaks are expected to be small and can be contained with SRPs 1-3. In outbreaks with increased transmissibility or in the presence of insecurity, rapid scale-up to SRP 4 is likely to save lives and be cost-effective.