Projecting health and economic impacts of Lassa vaccination campaigns in West Africa

Background: Lassa fever is a zoonotic disease identified by the World Health Organization (WHO) as having pandemic potential. Estimates of the health-economic impacts of vaccination are needed to guide vaccine investments. Methods: We estimated rates of Lassa virus (LASV) infection across West Africa, quantified the health-economic burden of disease and evaluated impacts of a series of vaccination campaigns. We also modelled the emergence of "Lassa-X" - a hypothetical pandemic LASV variant - and evaluated impacts of the 100 Days Mission, a pandemic response initiative aimed at delivering vaccines within 100 days of such a pathogen emerging. Findings: We estimated 2.7M (95% uncertainty interval: 2.1M-3.4M) LASV infections, 23.7K (14.9K-34.6K) hospitalisations and 3.9K (1.3K-8.3K) deaths annually, resulting over ten years in 2.0M (793.8K-3.9M) disability-adjusted life-years (DALYs) and $1.6B ($805.1M-$2.8B) in societal costs (International dollars 2021). Reaching 80% vaccine coverage in WHO-classified "endemic districts" and 5% coverage elsewhere with a vaccine 70% effective against disease prevented 3.3K (1.1K-7.0K) deaths, 164.1K (66.7K-317.7K) undiscounted DALYs and $128.2M ($67.2M-$231.9M) in discounted societal costs over ten years, thus averting approximately 11%-28% of DALYs in endemic countries. In the event of Lassa-X emerging, achieving 100 Days Mission vaccination targets averted approximately 22% of DALYs given a vaccine 70% effective against disease and 74% of DALYs given a vaccine 70% effective against both infection and disease. Interpretation: Vaccination will help alleviate Lassa fever's health-economic burden. Investing in Lassa vaccination now may help prepare against potential future variants with pandemic potential. Funding: Coalition for Epidemic Preparedness Innovations. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The Coalition for Epidemic Preparedness Innovations (CEPI) commissioned this analysis and CEPI internal Lassa fever experts were involved in study design by providing knowledge on input parameters and fine-tuning of realistic scenarios for vaccine rollout. An earlier version of this work was provided as a report to CEPI. ### 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 All underlying data and code for this article are available at www.github.com/drmsmith/lassaVac/