IAVI begins first-in-human Phase 1 trial of single-dose Marburg virus vaccine candidate

• No vaccines are approved specifically for the prevention of Marburg virus disease
• Marburg virus disease outbreaks seem to be increasing in frequency. Three outbreaks have occurred in sub-Saharan Africa in the past 18 months.
• The disease has an average case-fatality rate of about 65%.[1]
• Marburg virus is determined by the Department of Homeland Security to present a material threat to U.S. national security and is a Public Health Emergency Medical Countermeasures Enterprise high-priority threat.[2]

NEW YORK, NY — April 6, 2026 — IAVI, a global nonprofit biomedical research organization, announced today that the first participants have been vaccinated with a Marburg virus (MARV) vaccine candidate in a Phase 1 clinical trial in the U.S.

Known as IAVI C104 (NCT07425821), this first-in-human study is designed to evaluate the safety and immunogenicity of IAVI’s investigational rVSV∆G-MARV-GP vaccine candidate. In nonclinical studies, the vaccine candidate has generated consistently strong efficacy results. A single intramuscular vaccination with rVSV∆G-MARV-GP in nonclinical studies protected 100% against lethal challenge with Marburg virus.[3]

“IAVI C104 represents an important step toward generating the data needed for eventual regulatory approval of IAVI’s Marburg vaccine candidate,” said Mark Feinberg, M.D., Ph.D., president and CEO of IAVI. “In parallel with this trial, we will continue accelerating efforts toward the availability of candidate vaccine doses for evaluation during and ahead of Marburg outbreaks in sub-Saharan Africa with key collaborators. We’re grateful to our funder for its support of this trial and to the trial volunteers and partners.”

IAVI C104 takes place at several U.S. locations. The study is placebo-controlled, randomized, and observer-blind in design. The study vaccine will be administered intramuscularly at four dosage levels. Approximately 112 healthy adults will be enrolled and followed for six months after vaccination to monitor participant safety and to evaluate their immune responses to the vaccine candidate, which will be assessed using assays developed by IAVI scientists.

About Marburg virus and Marburg virus disease (MVD)

Marburg virus (from the Filoviridae family) causes severe febrile illness, sometimes with hemorrhaging, and often leads to death. A recent estimate of the average case fatality rate (CFR) among MVD patients is greater than 65%, though CFRs in some outbreaks have been as high as 80-90%.[1,4] The largest outbreak to date was in Angola in 2004-05, resulting in 252 cases and 227 deaths.[4] The most recent MVD outbreak – causing 14 cases and 9 deaths in Ethiopia – is believed to have begun in October 2025 and was declared over in January 2026.[5] Critically, MVD outbreaks appear to be increasing in frequency; of 17 outbreaks reported in sub-Saharan Africa since the virus was discovered (about 60 years ago), almost half have occurred in the last decade, and three in the last 18 months.[4] MVD is also increasingly emerging in previously unaffected countries, with recent outbreaks in Rwanda and Ethiopia being key examples [5,6].

About the vaccine candidate and the rVSV platform

The MARV vaccine candidate being evaluated in the IAVI C104 clinical trial uses the same recombinant vesicular stomatitis virus (rVSV) viral vector platform as ERVEBO, Merck’s single-dose Ebola virus (EBOV) vaccine, which is licensed in many countries including by the U.S. FDA. ERVEBO has been used extensively to vaccinate adults and children in Ebola outbreaks. Single-dose vaccines are especially valuable in outbreak situations because they allow rapid protection of at-risk populations without the logistical challenges of multidose follow-up.

rVSV is the platform technology underlying IAVI’s growing portfolio of emerging infectious disease (EID) vaccine candidates. In addition to the MARV vaccine candidate, IAVI’s rVSV-based EID portfolio includes a Sudan virus vaccine candidate supported by BARDA, a Lassa fever virus vaccine candidate currently in a Phase 2a trial and supported by the Coalition for Epidemic Preparedness Innovations and the European & Developing Countries Clinical Trials Partnership, and a Crimean Congo hemorrhagic fever virus vaccine candidate.

Using a shared viral vector platform streamlines vaccine development by enabling application of existing knowledge, clinical data, and manufacturing processes across multiple candidates. This approach has the potential to significantly accelerate response timelines during outbreaks while reducing costs and operational complexity.

Much of the research and development on IAVI’s rVSV platform is performed at the IAVI Vaccine Design and Development Lab (DDL) in Jersey City, New Jersey. Since its founding in 2008, the IAVI DDL has become one of the world’s leading viral vector vaccine research and development labs, known for innovation and generation of novel vaccine design concepts.

IAVI holds a nonexclusive license to the rVSV vaccine candidates from the Public Health Agency of Canada (PHAC). The vector was developed by scientists at PHAC’s National Microbiology Laboratory.

Funding

This project has been supported in whole or in part with federal funds from the U.S. Department of Health and Human Services; Administration for Strategic Preparedness and Response; Biomedical Advanced Research and Development Authority (BARDA), under contract number 75A50121C00077. The Defense Threat Reduction Agency (DTRA) of the U.S. Department of War (DOW) supported preclinical work on this vaccine candidate.

Funders who have made the development of IAVI’s rVSV-vectored vaccine candidates possible include the Gates Foundation; the Government of Canada; the Danish Ministry of Foreign Affairs; the Government of Japan; the Irish Department of Foreign Affairs and Trade; the Netherlands Ministry of Foreign Affairs; the Norwegian Agency for Development Cooperation; the U.K Department for International Development; the U.S. National Institutes of Health; and through the generous support of the American people from the former United States Agency for International Development.

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[1] Tian TT, Li AQ, Huang XX, Li JD. [Epidemiological characteristics of Marburg virus disease: A systematic review]. Zhonghua Liu Xing Bing Xue Za Zhi. 2025 Aug 10;46(8):1459-1467. Chinese. doi: 10.3760/cma.j.cn112338-20250206-00069. PMID: 40854777.

[2] Administration for Strategic Preparedness Response. PHEMCE priority threats.

[3] Cooper CL, Morrow G, Yuan M, Coleman JW, Hou F, Reiserova L, Li SL, Wagner D, Carpov A, Wallace-Selman O, Valentin K. Nonhuman primates are protected against Marburg virus disease by vaccination with a vesicular stomatitis virus vector-based vaccine prepared under conditions to allow advancement to human clinical trials. Vaccines. 2022 Sep 21;10(10):1582.

[4] Centers for Disease Control and Prevention. History of Marburg outbreaks.

[5] Al-Tawfiq JA. Ethiopia’s first Marburg virus outbreak – Implications for emerging hemorrhagic fevers in Africa. New Microbes New Infect. 2025;68:101677.

[6] Sibomana O, Hakayuwa CM, Munyantore J. Marburg virus reaches Rwanda: how close are we to a vaccine solution? International Journal of Infectious Diseases. 2025 Apr 1;153:107371.

[7] Centers for Disease Control and Prevention. Marburg outbreak in Ethiopia: Current situation. Jan. 26, 2026.

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IAVI Media Contact
Karie Youngdahl
Head, Global Communications
kyoungdahl@iavi.org