Sabin Vaccine Institute Completes Enrollment in All Phase 2 Clinical Trials for cAd3-Marburg Vaccine and cAd3-Sudan Ebolavirus Vaccine

Washington, D.C. - The Sabin Vaccine Institute (Sabin) has completed enrollment in all six Phase 2 clinical trials for its cAd3-Marburg Vaccine and its cAd3-Sudan Ebolavirus Vaccine to assess safety, tolerability, and immunogenicity.

Phase 2 clinical trials to evaluate the safety and immunogenicity of the two monovalent vaccines, both on the cAd3 platform, began in healthy volunteers in Africa in 2023 and in the United States in 2025. The African trials, with sites in Kenya and Uganda, completed participant follow-up last year and reporting activities are progressing. The U.S. trials completed enrollment last month. In addition, Sabin's cAd3-Marburg Vaccine has been used in Phase 2 rapid response outbreak clinical trials in Africa - more than 1,700 participants enrolled in 2024 during an outbreak in Rwanda, and more than 500 participants enrolled beginning last December for Ethiopia's first-ever Marburg outbreak.

Altogether, more than 2,800 trial participants have received Sabin's cAd3-Marburg Vaccine or cAd3-Sudan Ebolavirus Vaccine, and no significant safety concerns have been reported. Results from cAd3-Marburg Vaccine and cAd3-Sudan Ebolavirus Vaccine nonclinical studies indicate that the vaccines are safe and elicit rapid, robust protective immune responses.

Once rare, Marburg Virus Disease outbreaks have increased in Africa in recent years, with incidents reported in 2023 in Tanzania and Equatorial Guinea, in 2024 in Rwanda, and in 2025 in Tanzania and Ethiopia. Sudan Virus Disease outbreaks occurred in Uganda in 2022 and 2025. The diseases are transmitted from fruit bats to humans, spreading from person to person through contact with infected bodily fluids.

"Increasing outbreaks add urgency to the development of vaccines for these lethal diseases," says Sabin Chief Executive Officer Amy Finan. "Sabin continues to make steady progress on the milestones required for licensure of our vaccine candidates."

Why This Matters

There are no licensed vaccines for protection against disease caused by Marburg virus or the Sudan virus strain of Ebola. Both are highly contagious hemorrhagic fever diseases that can have a high fatality rate of up to 88%.

In addition, global attention to pandemic preparedness and health security has led to calls for preventive measures. At the recent Munich Security Conference, The Coalition for Epidemic Preparedness Innovations (CEPI) called epidemic and pandemic risk "a defining security challenge of our generation." Gavi, the Vaccine Alliance, named Marburg virus one of the top six global health threats of 2026.

What's Next

"We are currently analyzing the immunogenicity samples from the clinical trials in Africa, and we expect to have initial findings this year," says Sabin President of Research & Development Kelly Warfield. "As we bring all our Phase 2 clinical trials to conclusion, we are also in preliminary planning stages for a much larger Phase 3 trial for each vaccine."

Click these links for more information about the African cAd3-Marburg Vaccine trial, the U.S. cAd3-Marburg Vaccine trial, the African cAd3-Sudan Vaccine trial, the U.S. cAd3-Sudan Vaccine trial. and the cAd3-Marburg Vaccine Rwanda and Ethiopia outbreak trials.

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 numbers 75A50119C00055 and 75A50123C00010.

About the Sabin Vaccine Institute

The Sabin Vaccine Institute is a leading advocate for expanding vaccine access and uptake globally, advancing vaccine research and development, and amplifying vaccine knowledge and innovation. Unlocking the potential of vaccines through partnership, Sabin has built a robust ecosystem of funders, innovators, implementers, practitioners, policy makers, and public stakeholders to advance its vision of a future free from preventable diseases. As a non-profit with three decades of experience, Sabin is committed to finding solutions that last and extending the full benefits of vaccines to all people, regardless of who they are or where they live. At Sabin, we believe in the power of vaccines to change the world. For more information, visit www.sabin.org and follow us on LinkedIn, @Sabin Vaccine Institute.

About the cAd3 Platform

In August 2019, Sabin announced exclusive agreements with GSK for Sabin to advance the development of the prophylactic candidate vaccines against the deadly Zaire ebolavirus, Sudan virus, and Marburg virus. The three candidate vaccines were initially developed collaboratively by the U.S. National Institutes of Health and Okairos, which was acquired by GSK in 2013. The candidate vaccines, based on GSK's proprietary cAd3 (Chimpanzee Adenovirus Type 3) platform, were further developed by GSK, including the Phase 2 development for the Zaire ebolavirus vaccine. Under the agreements between GSK and Sabin, Sabin exclusively licensed the technology for all three candidate vaccines and acquired certain patent rights specific to these vaccines. Sabin is developing the cAd3-Marburg Vaccine and cAd3-Sudan Vaccine, both are in Phase 2 clinical trials in the U.S. and Africa.