Cost-effectiveness of geographically targeted versus ring vaccination campaigns in response to an outbreak of Ebola Virus Disease

Abstract For response to an outbreak of Ebola Virus Disease (EVD), the World Health Organisation (WHO) guidelines recommend vaccination of any contacts and contacts-of-contacts of identified EVD cases, also known as ring vaccination. However this standard response can be challenging to implement in remote regions or conflict zones. In recent outbreaks, response efforts have also tried blanket vaccination in the immediate vicinity of the homes and workplaces of identified cases, also known as geographically targeted vaccination. The relative effectiveness of these deployment strategies is difficult to study empirically, and modelling work to date has been limited. In this study, we use a spatially explicit individual-based stochastic simulation to model an EVD epidemic and public health response using either ring or geographically targeted vaccination alongside standard response activities. We explore a wide range of outbreak scenarios and response levels. Overall, we find little difference between ring or geographically targeted vaccination for either health or cost outcomes; the quality of surveillance and effectiveness of standard response activities are much larger drivers. However, vaccination does provide incremental benefit in combination with those activities, and the preferred strategy changes depending how well non-pharmaceutical activities are executed. Ring vaccination provides more incremental benefit on top of otherwise effective response activities (e.g. rapid and high ascertainment of contacts) but geographically targeted vaccination is better when those activities are less effectively delivered. These findings are relevant to policy makers deciding how to most effectively and cost-effectively deploy EVD vaccines in resource-limited and often challenging outbreak settings. Competing Interest Statement KH and AC received personal fees from Munich Re for work unrelated to this project. Funding Statement GNG, JES, WH, NMF, KH and AC acknowledge funding from the MRC Centre for Global Infectious Disease Analysis (reference MR/X020258/1), funded by the UK Medical Research Council (MRC). This UK funded award is carried out in the frame of the Global Health EDCTP3 Joint Undertaking. NMF and KH acknowledge funding by Community Jameel. The authors alone are responsible for the views expressed in this publication and they do not necessarily represent the decisions, policy or views of the WHO. SR is currently seconded to UKHSA as Chief Data Officer. CABP contributed to this project via cooperative agreement CDC-RFA-FT-23-0069 from the CDC Center for Forecasting and Outbreak Analytics. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Footnotes Updated the author list whilst the manuscript is under WHO internal reveiew Data Availability The code used to produce these results is available at https://github.com/mrc-ide/ebolasim_public