The World Health Organization (WHO) has recommended adding two experimental vaccines designed to target the Bundibugyo virus to an ongoing clinical trial in the Democratic Republic of the Congo (DRC), subject to national approval.
According to a WHO statement published on November 4, the recommendation marks the first time vaccines specifically developed against the Bundibugyo virus will be evaluated during an outbreak caused by this strain.
The two candidates are ChAdOx1 BDBV, developed by the University of Oxford in collaboration with the Serum Institute of India, and mRNA-1469, developed by US pharmaceutical company Moderna.
Both were recommended for further clinical evaluation by WHO's independent Technical Advisory Group on Candidate Vaccine Prioritization following a review of available preclinical and early clinical evidence. The group's November 4 meeting report confirms its unanimous recommendation to include both candidates in the Phase 2/3 trial.
The vaccines will enter the study after receiving the necessary approvals from the DRC's national authorities. The recommendation does not constitute approval for general public use.
The trial, known as Tumaini, is led by the DRC's National Institute of Biomedical Research (INRB), in cooperation with the University of Antwerp, WHO, Epicentre, Médecins Sans Frontières, the Institute of Tropical Medicine in Antwerp and the Africa Centres for Disease Control and Prevention.
Tumaini uses a ring-vaccination approach, in which people who have been in contact with confirmed cases of Bundibugyo virus disease are enrolled for vaccination. Four vaccination rings have already been established, with additional groups being prepared, according to WHO.
The study initially included Ervebo, a vaccine licensed against the Zaire ebolavirus species. Its effectiveness against the Bundibugyo virus has not been established and is now being assessed within the trial.
The distinction is important because Bundibugyo and Zaire are different species of Ebola virus. There is currently no vaccine specifically licensed to prevent disease caused by the Bundibugyo virus, according to WHO.
The current outbreak has prompted broader research into preventive vaccines and potential treatments. In May, WHO experts identified several candidate therapies for clinical evaluation, including the monoclonal antibodies MBP134 and maftivimab, as well as the antiviral drug remdesivir. An additional study is examining obeldesivir for post-exposure prevention.
WHO's Research and Development Blueprint and Health Emergencies Programme support the research, while the Coalition for Epidemic Preparedness Innovations (CEPI) has helped accelerate development of the vaccine candidates. WHO expects initial findings from the treatment studies in the coming months, while results from the vaccine trial are anticipated in early 2027.
Although the addition of the two candidates expands the scope of research, their safety and effectiveness against the Bundibugyo virus will need to be established through clinical trials. WHO has also stressed that vaccination alone cannot stop the outbreak, making surveillance, contact tracing, patient care and community engagement essential parts of the response.
According to the World Health Organization, as of November 3, the Democratic Republic of the Congo had recorded 10,668 confirmed cases of Bundibugyo virus disease, including 5,198 deaths, while 2,881 patients had recovered. The outbreak, first declared in Ituri Province on May 15, has spread to eight provinces and 67 health zones, with a confirmed case fatality ratio of approximately 49%. The WHO has classified the outbreak as a public health emergency of international concern.
