Will Lassa-X Cause a Pandemic

Since the disease was first documented in 1969, Lassa fever has become a public health risk in western Africa.

For the first time, researchers at the University of Liverpool and the University of Oxford have estimated the current burden of Lassa fever, projected the impacts of a Lassa fever vaccination program, and demonstrated how it may help avoid a future pandemic.

The World Health Organization (WHO) has expressed concerns that a Lassa-related virus could cause a global concern due to the lack of effective vaccines and treatments.

Published on August 28, 2024, this study estimates the health-economic burden of Lassa fever throughout West Africa and projects the impacts of a series of vaccination campaigns.

It suggests how vaccination could alleviate the burden and assist in pandemic preparedness.

These London-based researchers also model the emergence of ‘Lassa-X’—a hypothetical pandemic Lassa virus variant—and project impacts of achieving 100 Days Mission vaccination targets.

Their model predicted 2.7 million (95% uncertainty interval: 2.1–3.4 million) Lassa virus infections annually, resulting in 2.0 million (793,800–3.9 million) disability-adjusted life years (DALYs) over ten years.

A population-wide preventive campaign targeting WHO-classified ‘endemic’ districts was found to be the most effective vaccination strategy.

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.

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 two years, 100 Days Mission vaccination averted 22% of DALYs given a vaccine 70% effective against the disease, and 74% of DALYs given a vaccine 70% effective against both infection and disease.

As of late August 2024, several Lassa fever vaccine candidates are conducting clinical research.

The Coalition for Epidemic Preparedness Interventions funded this study, which was published in the journal Nature Medicine.