Lassa virus (LASV) disease is a zoonotic viral hemorrhagic fever endemic in West Africa and a World Health Organization priority pathogen. No approved vaccine exists for LASV, which kills an estimated 5,000 and sickens about 300,000 annually — though the true disease burden is not well characterized and believed to be much higher. A vaccine is urgently needed: Modeling data in Nature show that a vaccine could save thousands of lives and avert up to US$128 million in societal costs over 10 years.

As LASV’s geographic footprint expands due to climate change, urbanization and other factors, scientists are accelerating their vaccine research. LASV vaccine development’s largest funder is the Coalition for Epidemic Preparedness Innovations (CEPI). Their LASV portfolio includes six candidates, four of which have advanced to clinical trials. IAVI’s vesicular stomatitis virus (VSV)-based LASV vaccine candidate is the furthest along.

With VSV already the backbone of a licensed vaccine — Ervebo®, Merck’s Ebola Zaire vaccine — IAVI and partners are harnessing this proven vaccine platform technology to develop accessible vaccines for LASV and other priority pathogens. On Thursday at TropMed, collaborators from across LASV vaccine development gave a symposium to share study updates, including preclinical and Phase 1 clinical study results.

Swati Gupta, vice president and head of emerging infectious diseases and epidemiology, IAVI, and Melanie McCauley, Clinical Research Liaison for West Africa, the Henry M. Jackson Foundation for the Advancement of Military Medicine, Viral Disease Program at the Walter Reed Army Institute of Research, served as co-chairs.

Christian Happi, director, Institute of Genomics and Global Health, Redeemer’s University, described an epidemiological study conducted in Southern Nigeria to better understand the regional burden of LASV infection. Researchers gathered samples from humans and animals, leading to the identification of novel non-rodent reservoirs and additional prevalence and incidence data.

Kent Kester, executive director, vaccine research and development division, CEPI, provided an overview of the CEPI ENABLE program. This program includes the largest LASV observational study and primarily aims to fill epidemiological knowledge gaps to inform future clinical trial development.

Christopher Cooper, director, viral vaccines, IAVI Vaccine Design and Development Laboratory, shared promising results from CEPI-supported nonclinical studies of IAVI’s LASV vaccine candidate — most notably, a 100% survival rate among vaccinated animals challenged with LASV up to a year after vaccination.

Mark Kieh, principal investigator of the IAVI-sponsored Phase 1 clinical trial of IAVI’s Lassa fever vaccine candidate at PREVAIL in Liberia, presented findings from the CEPI-supported study conducted in the U.S. and Liberia. In both cohorts, the vaccine candidate was well tolerated and elicited strong immune responses with no safety signals detected. These data supported the advancement of the candidate into Phase 2 testing.

Johan Vekemans, Lassa fever vaccine project lead, IAVI, offered lessons learned and a look ahead at a planned Phase 2b clinical trial of IAVI’s LASV vaccine candidate in West Africa, also supported by the European and Developing Countries Clinical Trials Partnership, and preparations for a Phase 3 trial.

Together, these presentations offered a comprehensive end-to-end vision for access, preparedness, local scientific leadership and community engagement.