Lassa Fever Vaccine

Lassa Fever Vaccine Candidates 2025

The U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) have not approved vaccines for the Lassa fever virus (LASV). As of November 2025, four Lassa fever vaccine candidates (LASSARAB, INO-4500, MV-LASV, rVSV∆G-LASV-GPC, and EBS-LASV) have entered clinical trials.

Given its potential to cause a public health emergency of international concern, LASV is included in the World Health Organization (WHO) R&D Blueprint, a list of priority pathogens for which there is an urgent need for accelerated research, vaccine development, and countermeasures. The WHO has ranked Lassa (arenaviruses) as the most likely animal virus to spill over into humans ahead of Ebolavirus. A detailed estimate of the damage caused by LASV outbreaks, published in August 2024, has found that it infects 2.7 million people annually, ten times more than health agencies had previously assumed. Modelling research predicts that up to 600 million people could be at risk of Lassa fever infection by 2050, due to the combined effects of climate change and population growth.

The International AIDS Vaccine Initiative (IAVI) LASV vaccine candidate is conducting research (IAVI C105 and C102) to evaluate the Safety, Tolerability, and Immunogenicity of the rVSV∆G-LASV-GPC Vaccine in Adults and Children living in West Africa. As of 2025, Ghana, Liberia, and Nigeria are vaccinating volunteers. The Coalition for Epidemic Preparedness Innovations supported a Phase I (clinical trial IAVI C102). Batavia Biosciences manufactured the IAVI's LASV vaccine candidate in Leiden, the Netherlands.

rLASV/IGR-CD, developed by the Texas Biomedical Research Institute, The Scripps Research Institute, and the National Institute of Allergy and Infectious Diseases, incorporates both attenuation determinants and further enhances the vaccine's safety. Data published in November 2024 support the development of rLASV/IGR-CD as a live-attenuated LF vaccine with stringent safety features.

The Lassa fever vaccine candidate LASSARAB uses a deactivated rabies virus platform to deliver antigens to protect against the Lassa fever virus. Researchers from Thomas Jefferson University and the University of Maryland, Baltimore, have developed LASSARAB in collaboration with the United States Army Medical Research Institute of Infectious Diseases and the Geneva Foundation. The primary completion date of the Phase 1 study is 2026-03.

ChAdOx1-Lassa-GPC is a chimpanzee adenovirus-vectored vaccine candidate encoding the Josiah strain LASV glycoprotein precursor gene.

Themis Bioscience GmbH is a recombinant, live-attenuated, measles-vectored Lassa fever vaccine candidate (MV-LASV). In a first-in-human phase 1 trial, MV-LASV (V182-001) showed an acceptable safety and tolerability profile, and immunogenicity was unaffected by pre-existing immunity against the vector.

Inovio discontinued the development of product candidates targeting Lassa Fever (INO-4500) on November 17, 2022.

Lassa Fever Overview

Lassa fever (LF) is an acute viral hemorrhagic fever (VHF) caused by the Lassa virus. The natural reservoir for the LASV is the Mastomys natalensis rodent (African rat). Lassa virus is endemic in the West African countries of Benin, Ghana, Guinea, Liberia, Mali, Nigeria, and Sierra Leone. 

In epidemiological week 23 (June 2025), 146 new confirmed cases of Lassa fever, including one death, were reported from four states across Nigeria. During 2025, a cumulative total of 765 cases with 143 deaths (CFR 18.9 %) have been reported from 18 Nigerian states, mainly in Ondo, Bauchi, Edo, Taraba, and Ebonyi.

As of March 2025, Liberia has reported confirmed Lassa fever cases, with none in the latest update. Grand Bassa County remains the only area with active transmission of the disease. Since January 2022, the cumulative total stands at 186 confirmed cases, including 56 deaths (CFR 30%), with Bong, Nimba, and Lofa counties being the most affected historically.

Lassa Fever Vaccine News

December 16, 2024 – A vaccine candidate against the Lassa virus completely protected guinea pigs exposed to an otherwise lethal dose of the virus, reported researchers from Texas Biomedical Research Institute, The Scripps Research Institute, and The National Institute of Allergy and Infectious Diseases.

January 4, 2024 - Research findings defined a prefusion-stabilized GPC trimer, revealed an apex-situated site of vulnerability, and demonstrated that a cleavage-intermediate LASV trimer elicits LASV-neutralizing responses.

August 24, 2023 - Imunon, Inc. entered into a Cooperative Research and Development Agreement with the National Institute of Allergy and Infectious Diseases to evaluate the immunogenicity and efficacy of two IMUNON DNA-based Lassa vaccine candidates.

March 16, 023—The Lancet published a study that concluded that MV-LASV showed an acceptable frequency and tolerability and that immunogenicity seemed unaffected by pre-existing immunity against the vector. 

August 31, 022 – IAVI announced that volunteers at the PREVAIL clinical trial site at Redemption Hospital in Monrovia, Liberia, have been vaccinated with its novel vaccine candidate against LASV in a Phase 1 clinical trial.