The Sabin Vaccine Institute has launched a multi-site Phase 2 clinical trial in the United States for its Marburg virus vaccine candidate, administering initial doses to participants in Melbourne, Florida. This development marks a significant expansion of the organization's efforts to combat the deadly hemorrhagic fever, for which no approved vaccines currently exist.
The U.S. trial builds upon Sabin's ongoing Phase 2 testing in Kenya and Uganda, with preliminary findings from those African studies expected in the coming months. The advancement comes amid increasing frequency of Marburg outbreaks globally, highlighting the urgent need for preventative measures.
"Recent outbreaks highlight the urgent need to strengthen our defenses against this deadly and unforgiving disease," said Amy Finan, Sabin's Chief Executive Officer. "Sabin's Phase 2 clinical trials will generate essential data to move this vaccine closer to licensure — and offer a potentially life-saving tool where none exists."
Trial Design and Scope
The randomized, placebo-controlled, double-blind U.S. trial aims to recruit 200 volunteers aged 18 to 70 across four locations: Melbourne, Florida; Dallas, Texas; Huntsville, Alabama; and Peoria, Illinois. Researchers will evaluate safety and immunogenicity while monitoring vaccinated volunteers for a full year.
This expansion into U.S. testing complements Sabin's strategic approach to vaccine development. Kelly Warfield, Sabin's President of Research & Development, explained: "Conducting clinical trials in Africa is key to evaluating the vaccine in regions where Marburg and other filoviruses are most common or endemic. The U.S. trial will give us vital safety and immune response data for non-endemic populations, helping us better prepare for outbreaks and spread of this disease."
Real-World Application During Recent Outbreaks
The vaccine candidate has already seen emergency deployment during Rwanda's 2024 Marburg outbreak. Sabin supported an open-label Phase 2 clinical trial sponsored by the Rwanda Biomedical Centre by supplying the investigational vaccine to more than 1,700 individuals, primarily frontline healthcare workers. First doses arrived within nine days of the outbreak declaration.
Rwanda's outbreak ended on December 20, 2024, with a case fatality rate of 23% — significantly lower than the historical average of 50%. While multiple factors likely contributed to this reduced mortality, including improved surveillance and supportive care, the data from this emergency deployment will be shared with Sabin to support the vaccine's eventual licensure.
Tanzania subsequently declared a Marburg outbreak on January 20, 2025, which concluded on March 13.
Vaccine Technology and Development History
Sabin's Marburg vaccine candidate utilizes the cAd3 (Chimpanzee Adenovirus Type 3) platform, originally developed through collaboration between the U.S. National Institutes of Health and Okairos, which was later acquired by GSK in 2013. In August 2019, Sabin announced exclusive agreements with GSK to advance development of prophylactic candidate vaccines against Zaire ebolavirus, Sudan virus, and Marburg virus.
Phase 1 clinical and non-clinical studies have shown promising results for the single-dose investigational Marburg vaccine, demonstrating safety while eliciting rapid and robust immune responses.
Disease Background and Transmission
Marburg virus disease is caused by a filovirus in the same family as Ebola. It spreads through direct contact with blood or other bodily fluids of infected individuals. The disease is highly virulent and causes hemorrhagic fever with a historically high fatality rate.
Unlike many other infectious diseases, Marburg outbreaks have been increasing in frequency, creating urgency around vaccine development efforts. The lack of approved vaccines makes preventative measures particularly challenging during outbreaks.
Funding and Future Directions
The Marburg vaccine trials are supported by the Biomedical Advanced Research and Development Authority (BARDA), part of the Administration for Strategic Preparedness and Response within the U.S. Department of Health and Human Services. BARDA and Sabin began their partnership in September 2019 to develop monovalent vaccine candidates for both Marburg virus and Sudan virus diseases. To date, Sabin has received approximately $252 million in contract awards from BARDA for these development efforts.
A parallel Phase 2 clinical trial for Sabin's Sudan virus vaccine is currently underway in Uganda and Kenya, with plans to test the cAd3 Sudan vaccine candidate among adult volunteers in the U.S. later this year.
For those interested in learning more about the ongoing trials, information is available through ClinicalTrials.gov (NCT06620003 for the U.S. trial and NCT05817422 for the Uganda and Kenya trial) and the Pan African Clinical Trials Registry (PACTR202306534727467 for the Uganda and Kenya trial).
