Cost-effectiveness of targeted geographic versus ring vaccination campaigns in response to an outbreak of Ebola Virus Disease caused by Orthoebolavirus zairense

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Abstract Background WHO recommends ring vaccination (RV) of Ebola virus disease (EVD) case contact chains to contain outbreaks of Orthoebolavirus zairense . However, this strategy can falter in remote or conflict-affected settings where effective contact tracing is challenging. Targeted geographic vaccination (TGV) – immunising everyone near an EVD case’s location without requiring contact tracing – has been implemented as an alternative. We compare the epidemiological impact and cost-effectiveness of TGV versus RV under diverse outbreak scenarios. Methods We extended a spatially-explicit individual-based stochastic EVD transmission model calibrated to outbreaks in the Democratic Republic of the Congo. We simulated outbreaks varying both epidemiological and operational parameters. We evaluated vaccination strategies on total cases, deaths, epidemic duration, vaccine doses used, and incremental net monetary benefit (INMB). Results No single strategy dominates in all scenarios. For better overall response performance, RV results in substantially fewer cases and deaths than TGV (approximately 20% fewer cases), requires fewer doses, and has higher INMB more frequently. Under pessimistic response assumptions, TGV slightly outperforms RV by preventing more infections, curbing the largest outbreaks, and using fewer doses, although the INMBs are similar between strategies. Interpretation Different operational contexts recommend different vaccination strategies. Overall, surveillance, contact tracing, and isolation have the most impact on Orthoebolavirus zairense outbreak control. Depending on response effectiveness, the preferred strategy for adding vaccination varies. Backed by effective case detection and management, RV appears the better approach. Under severe response constraints, TGV can be more effective.

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