๐ฉธ Lassa Fever Vaccine Tracker Dashboard
Updated July 2026. Tracking Lassa fever vaccine development to prevent viral hemorrhagic fever in West Africa. Lassa fever infects an estimated 300,000 people annually with about 5,000 deaths, primarily in Nigeria, Sierra Leone, Guinea, and Liberia. No licensed vaccine exists. Major 2024โ2026 progress: IAVI's rVSVฮG-LASV-GPC vaccine โ the world's first-ever Phase 2 Lassa vaccine trial โ became fully active across Ghana, Liberia, and Nigeria in early 2025, with approximately 612 participants (adults, adolescents, and children aged 2+, including people living with HIV) enrolled in the IAVI C105 study (NCT05868733). Primary completion is estimated December 2026. Phase 1 results published in NEJM showed sustained immune responses in over 100 adults from a single dose, with the vaccine using the same rVSV backbone as the licensed Merck Ebola vaccine (Ervebo). The LEAP4WA consortium โ funded by EDCTP and CEPI โ is advancing preparations for a Phase 2b trial of rVSVฮG-LASV-GPC in 2026. CEPI has invested in five Lassa vaccine candidates; two remain in active clinical development (IAVI's rVSV and Oxford's ChAdOx1 candidate in Phase 1). This tracker monitors the complete Lassa fever vaccine pipeline.
Lassa Fever Vaccines by Development Phase
๐งฌ Phase 2 Clinical Trials
Technology
rVSV vector expressing LASV glycoprotein
Phase 1 Results
Safe, strong antibody response
Trial Location
Nigeria, Liberia
Details: rVSV-LASV uses the same proven vesicular stomatitis virus platform as the licensed Ebola vaccine (Ervebo). Phase 1 trials (NCT03805984) in 60 healthy adults in Liberia showed excellent safety and robust antibody responses against Lassa virus glycoprotein. The vaccine induced neutralizing antibodies in 95% of participants by day 28. Phase 2 trials launched in 2023 in Nigeria and Liberia are assessing immunogenicity, safety, and durability of immunity in ~200 adults in endemic areas. Single-dose regimen. CEPI (Coalition for Epidemic Preparedness Innovations) provided $23 million funding.
Current Status: Phase 2 ongoing in West Africa. If successful, could advance to Phase 3 efficacy trials in endemic regions by 2025-2026. Represents most advanced Lassa fever vaccine candidate globally.
Technology
MVA vector + LASV antigens
Regimen
Two-dose schedule
Phase 1 Results
Well-tolerated, immunogenic
Description: MVA-LASV leverages Bavarian Nordic's Modified Vaccinia Ankara platform, proven safe in immunocompromised individuals. Phase 1 trials demonstrated safety and immunogenicity with two-dose regimen (0, 28 days). Vaccine encodes Lassa virus glycoprotein complex and nucleoprotein. Phase 2 studies evaluating optimal dosing and immune persistence. MVA platform advantages: non-replicating, safe in HIV+ individuals, established manufacturing.
Current Status: Phase 2 ongoing. Bavarian Nordic has extensive experience with MVA-based vaccines including smallpox (JYNNEOS) and Ebola vaccines.
๐งช Phase 1 Clinical Trials
Developer
MHRP/NIH/USAMRIID
Technology
VLP (glycoprotein + Z matrix)
Preclinical
Protective in guinea pigs, NHP
Description: ML29 VLP vaccine developed by US Military HIV Research Program (MHRP) in collaboration with NIH and USAMRIID. VLPs contain Lassa virus glycoprotein complex and Z matrix protein but no viral genome. Demonstrated complete protection in guinea pig and non-human primate challenge studies. Phase 1 trials assess safety, tolerability, and immunogenicity in healthy adults. Two-dose regimen with adjuvant.
Technology
mRNA-LNP platform
Advantage
Rapid manufacturing, scalable
Description: Moderna's mRNA vaccine encodes Lassa virus glycoprotein precursor (GPC). Leverages proven COVID-19 mRNA-LNP technology for rapid response to emerging threats. Early-phase trials initiated in 2023 assessing safety and immunogenicity. Single or two-dose regimen under investigation. Advantages include rapid manufacturing (weeks vs months), thermostability improvements, and potential for multivalent formulations covering Lassa and other arenaviruses.
Technology
DNA plasmid + electroporation
Target
Cellular + humoral immunity
Advantage
Thermostable, long shelf life
Description: DNA vaccine encoding Lassa virus glycoproteins delivered via electroporation to enhance uptake and immunogenicity. Phase 1 safety trials in healthy volunteers. DNA platform advantages: stable at room temperature, no cold chain required (critical for West Africa), induces both CD4+ and CD8+ T cell responses alongside antibodies. Preclinical studies showed protection in animal models.
๐ฌ Preclinical Development
Description: Self-amplifying RNA vaccines encoding Lassa glycoprotein with built-in replication machinery. Requires 10-100x lower doses than conventional mRNA. Preclinical studies in mice and guinea pigs demonstrate robust neutralizing antibody responses and protection against lethal Lassa virus challenge. Advantages: dose-sparing, enhanced immunogenicity, potential for single-dose regimen.
Description: ChAdOx1 or ChAdOx2 vectors expressing Lassa virus antigens. Same platform as COVID-19 AstraZeneca vaccine. Non-human primate studies show strong cellular and humoral immunity. Single-dose efficacy demonstrated in animal models. Could be manufactured at scale in existing facilities.
Description: Multivalent vaccine targeting Lassa fever plus other pathogenic arenaviruses (Junรญn, Machupo, Guanarito, Sabiรก - causative agents of Argentine, Bolivian, Venezuelan, and Brazilian hemorrhagic fevers). VLP or mRNA platform encoding glycoproteins from multiple arenaviruses. Animal studies demonstrate broad cross-protective immunity.
Description: Recombinant Lassa glycoprotein displayed on ferritin or other nanoparticle scaffolds with adjuvant (Matrix-M, AS01). Highly stable, induces potent neutralizing antibodies. Guinea pig studies show dose-dependent protection. Advantages: no live components, suitable for immunocompromised, stable at 2-8ยฐC.
Description: Live-attenuated Lassa virus reassortant (ML29 strain) combining attenuated segments with immunogenic glycoproteins. Single-dose protection in non-human primates. Concerns about reversion to virulence and safety in immunocompromised limit development. Requires high biosafety manufacturing (BSL-4). Historical approach with proven efficacy but safety challenges.