Health and economic impacts of Lassa vaccination campaigns in West Africa

Abstract Lassa fever is a zoonotic disease identified by the World Health Organization (WHO) as having pandemic potential. This study estimates the health-economic burden of Lassa fever throughout West Africa and projects impacts of a series of vaccination campaigns. We also model the emergence of ‘Lassa-X’—a hypothetical pandemic Lassa virus variant—and project impacts of achieving 100 Days Mission vaccination targets. Our model predicted 2. 7 million (95% uncertainty interval: 2. 1–3. 4 million) Lassa virus infections annually, resulting over 10 years in 2. 0 million (793, 800–3. 9 million) disability-adjusted life years (DALYs). The most effective vaccination strategy was a population-wide preventive campaign primarily targeting WHO-classified ‘endemic’ districts. Under conservative vaccine efficacy assumptions, this campaign averted 20. 1 million (8. 2–39. 0 million) in lost DALY value and 128. 2 million (67. 2–231. 9 million) in societal costs (2021 international dollars () ). Reactive vaccination in response to local outbreaks averted just one-tenth the health-economic burden of preventive campaigns. In the event of Lassa-X emerging, spreading throughout West Africa and causing approximately 1. 2 million DALYs within 2 years, 100 Days Mission vaccination averted 22% of DALYs given a vaccine 70% effective against disease and 74% of DALYs given a vaccine 70% effective against both infection and disease. These findings suggest how vaccination could alleviate Lassa fever’s burden and assist in pandemic preparedness.