Lassa virus vaccine

A platform approach to vaccine development

All of IAVI’s emerging infectious disease vaccines use the same technology behind Merck’s Ebolavirus vaccine, ERVEBO®, which is licensed in more than a dozen countries.

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Lassa virus (LASV) vaccines: Bridging the gap for an endemic threat

IAVI and our partners are developing a single-dose vaccine candidate for protection against LASV. No vaccine is yet approved to prevent Lassa fever.  

LASV (family Arenaviridae) causes an acute viral hemorrhagic illness called Lassa fever. An estimated 5,000 people die each year from Lassa fever, and about 300,000 people fall ill across West Africa annually – though the true disease burden is thought to be much higher. Given its potential to cause a public health emergency of international concern, LASV is included in the World Health Organization’s Pathogens prioritization: a scientific framework for epidemic and pandemic research, which identifies pathogens for which there is an urgent need for accelerated R&D and countermeasures. 

IAVI’s LASV vaccine candidate (rVSVΔG-LASV-GPC) is currently in Phase 2a clinical development (IAVI C105, NCT05868733). It is the most advanced LASV candidate to date. In this study, researchers are evaluating the vaccine candidate’s safety, tolerability, and immunogenicity at two different dosage levels in adults, including people living with HIV, as well as in adolescents and in children two years of age and older. The vaccine candidate was well-tolerated and immunogenic among participants in IAVI’s Phase 1 LASV vaccine trial (IAVI C102, NCT04794218), which was conducted in the U.S. and in Liberia. Robust immune responses appear to be sustained for up to one year after vaccination. 

IAVI’s Phase 2a LASV vaccine clinical trial is funded by the Coalitions for Epidemic Preparedness Innovations (CEPI) and the European and Developing Countries Clinical Trials Partnership. Earlier work was funded by CEPI.

More about LASV

• No vaccines or specific treatments available 

• Transmitted via animal reservoir (rats) and direct contact with a symptomatic person or their infectious bodily fluids 

• Causes a range of symptoms including flu-like symptoms; 20% of people with LASV infection develop serious symptoms including widespread bleeding and major organ failure 

• Some survivors experience permanent deafness 

Fact sheet

Regional commitment

In 2025, West African Ministers of Health pledged their joint commitment to advance the development of, and readiness for, much-needed vaccines against Lassa fever in recognition of the significant threat to regional health security posed by the disease.

The pledge includes supporting the development of rVSVΔG-LASV-GPC through a collaborative co-funding approach and joint action to mobilize and secure resources through advocacy and regional coordination. 

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News & Articles

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Features

Fast facts about IAVI’s contributions to fighting Lassa fever in West Africa

September 11, 2025

IAVI and partners in Nigeria, Liberia, and Ghana are currently vaccinating volunteers in the Phase 2a IAVI C105 clinical trial of IAVI’s Lassa virus (LASV) vaccine candidate. The study is designed to evaluate the vaccine candidate’s safety, tolerability, and immunogenicity at two different dosage levels in adults.   Read more about how we are contributing to the fight […]

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Features

Frequently asked questions: Lassa fever

September 11, 2025

Exactly what is Lassa fever? Lassa virus (LASV) causes seasonal outbreaks across West Africa, and the World Health Organization (WHO) has identified it in the Pathogen Prioritization framework as a top emerging pathogen likely to cause public health emergencies of international concern. IAVI and our partners are developing a single-dose LASV vaccine candidate as part of […]

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Press Release

West African leaders commit to advance Lassa fever vaccine for the region

September 09, 2025

West African health ministers together with leaders from IAVI, and the Coalition for Epidemic Preparedness Innovations at a meeting to advance Lassa fever vaccine development during the 2nd Lassa Fever International Conference in Abidjian, Côte d’Ivoire, on September 8, 2025.   ABIDJAN, COTE D’IVOIRE — On September 8, 2025, Ministers of Health from across the region gathered for high-level talks convened by the West African Health Organisation (WAHO) and Dr. Muhammad Ali Pate, the Coordinating Minister of Health and Social Welfare of Nigeria, as co-leads of the Lassa f

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Features

Findings from papers in eBioMedicine advance development of IAVI’s single-dose Lassa fever vaccine candidate 

April 16, 2025

Lassa fever is a viral hemorrhagic fever (VHF) associated with a high case fatality rate[1]. The disease is caused by the arenavirus Lassa virus (LASV), a priority pathogen as ranked by organizations such as the World Health Organization, U.S. National Institutes of Health, and the Coalition for Epidemic Preparedness Innovations (CEPI). Traditionally, estimates have ranged […]

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Press Release

Participants in Nigeria vaccinated in first-ever Phase 2 Lassa fever vaccine clinical trial, sponsored by IAVI

April 04, 2024

Key takeaways: Participants at HJF Medical Research International in Abuja, Nigeria, have been vaccinated in the first Phase 2 clinical trial of a Lassa fever virus (LASV) vaccine candidate to date, according to IAVI, a nonprofit scientific research organization and the trial sponsor. The study (IAVI C105/PREVAIL15) is funded by CEPI, an innovative global partnership […]

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Press Release

IAVI announces first vaccinations at Liberia site in Phase 1 clinical trial of Lassa fever vaccine candidate

August 31, 2022

NEW YORK – AUGUST 31, 2022 – IAVI, a nonprofit scientific research organization, announces that volunteers at the PREVAIL clinical trial site at Redemption Hospital (RH1) in Monrovia, Liberia, have been vaccinated with IAVI’s novel vaccine candidate against Lassa fever virus (LASV) in a Phase 1 clinical trial, named IAVI C102, supported by the Coalition […]

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