Health and economic impacts of Lassa vaccination campaigns in West Africa

Abstract

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.