Vaccine Info

MV-LASV Lassa Fever Vaccine

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Last reviewed
April 15, 2023
Fact checked by
Robert Carlson, MD

MV-LASV Lassa Fever Vaccine April 2023

MV-LASV is a recombinant, live-attenuated, viral vectored Lass fever vaccine candidate based on the backbone of the measles Schwarz virus strain for prophylaxis of Lassa infection. On October 29, 2019, Themis Bioscience and the Coalition for Epidemic Preparedness Innovations announced the first administration to healthy volunteers in a Phase 1 clinical trial with Themis’ vaccine candidate against Lassa fever. 

On March 16, 2023, The Lancet published: Immunogenicity, safety, and tolerability of a recombinant measles-vectored Lassa fever vaccine: a randomized, placebo-controlled, first-in-human trial. Interpretation: MV-LASV showed an acceptable safety and tolerability profile, and immunogenicity seemed to be unaffected by pre-existing immunity against the vector. MV-LASV is, therefore, a promising candidate for further development. The Coalition for Epidemic Preparedness Innovations funded this phase 1 study.

According to the World Health Organization, LF vaccines should be cost-effective, affordable in endemic areas, and stable for a reasonable time without extensive cold chain facilities.

In June 2020, Merck completed the acquisition of Themis, a privately-held company focused on vaccines and immune-modulation therapies for infectious diseases and cancer.

MV-LASV Indication

MV-LASV vaccine candidate is indicated for at-risk populations during outbreaks of Lassa Fever, an emerging infectious disease. Lassa fever is an acute viral hemorrhagic disease caused by the Lassa virus (LASV). It is endemic in West Africa and infects about 300,000 people yearly, leading to approximately 5000 deaths annually. Therefore, the World Health Organization has listed the development of the LASV vaccine as a priority since 2018. 

MV-LASV Dosage

MV-LASV is administered in two different dose levels by intramuscular. injection. The aim is to investigate the safety, tolerability, and immunogenicity of MV-LASV after administering two different dose levels of MV-LASV. 

MV-LASV Clinical Trial

Clinical Trial NCT04055454: A Trial to Evaluate the Optimal Dose of MV-LASV - The trial is registered with the European Union Drug Regulating Authorities Clinical Trials Database, 2018-003647-40, and is complete.

Findings - Between September 26, 2019, and January 20, 2020, 60 participants were enrolled and assigned to receive placebo (n=12) or MV-LASV (n=48). All 60 participants received at least one study treatment. Most adverse events occurred during the treatment phase, and frequencies of total solicited or unsolicited adverse events were similar between treatment groups, with 96% of participants in the low-dose group, 100% of those in the high-dose group, and 92% of those in the placebo group having any solicited adverse event (p=0·6751) and 76% of those in the low-dose group, 70% of those in the high-dose group, and 100% of those in the placebo group having any unsolicited adverse event (p=0·1047). The only significant difference related to local solicited adverse events, with higher frequencies observed in groups receiving MV-LASV (24 [96%] of 25 participants in the low-dose group; all 23 [100%] participants in the high-dose group) than in the placebo group (6 [50%] of 12 participants; p=0·0001, Fisher-Freeman-Halton test). Adverse events were mainly of mild or moderate severity, and no serious adverse events were observed. MV-LASV also induced substantial concentrations of LASV-specific IgG (geometric mean titre 62·9 EU/ml in the low-dose group and 145·9 EU/ml in the high-dose group on day 42).

Clinical Trials

No clinical trials found