Independent advisers have recommended adding two experimental vaccines designed specifically for the Bundibugyo virus to an Ebola study under way in the Democratic Republic of the Congo.
The World Health Organisation said the candidates, known as ChAdOx1 and mRNA-1469, could enter the Tumaini trial after national approvals. The recommendation is not itself a regulatory approval, and neither candidate has been shown to protect people against the virus in this outbreak.
ChAdOx1 is being developed by the University of Oxford with the Serum Institute of India. The mRNA-1469 candidate is being developed by Moderna. An independent advisory group convened by the health organisation recommended both for further clinical evaluation after considering preclinical and early clinical evidence.
The companies were informed on Monday, the organisation said in its announcement on Wednesday. It expects results from the vaccine trial in early 2027, although that is an expectation rather than a confirmed date for findings.
A new stage for an existing study
The recommendation follows the start of Tumaini in Bunia, in the country’s north-eastern Ituri province. The first participant was vaccinated on 23 October. The study is led by the Congolese National Institute for Biomedical Research and the University of Antwerp, with national and international partners.
The two Bundibugyo-specific candidates had already been identified as possible additions to the study. The new development is the advisers’ recommendation that both be evaluated, subject to the required national approvals. It is not an announcement that vaccinations with either new candidate have already begun.
Tumaini is a phase 2/3 trial designed to assess the safety, immune response and effectiveness of vaccine candidates. Its adaptive structure allows more than one candidate to be examined within the same study, rather than requiring a wholly separate trial for each one.
The study uses a ring-vaccination approach, enrolling contacts of people with confirmed Bundibugyo virus disease. The World Health Organisation said four vaccination rings were already in place and several more were being prepared. The rings include contacts of people who became ill or died from Ebola.
Ervebo is the first vaccine being evaluated in the study. It is licensed against Ebola virus, also known as Zaire ebolavirus, but was not designed specifically for Bundibugyo. Researchers are assessing whether it offers protection against the virus responsible for the current outbreak; that protection has not been established.
The proposed additions address a different question: whether vaccines designed for Bundibugyo can safely protect people exposed to that virus. The health organisation said their evaluation would be the first time specifically designed candidates had been tested during an outbreak of the disease.
Research alongside the response
Bundibugyo is one of several viruses that can cause Ebola disease. There is no licensed vaccine specifically against it. The disease can spread through direct contact with the bodily fluids of an infected person or contaminated materials, and early supportive care can improve a patient’s chance of survival.
Finding a vaccine is only one part of the response. Health teams also work to identify infections, trace contacts, care for patients and support safe, dignified burials. Those measures continue while researchers gather evidence; the recommendation does not establish that transmission has stopped.
A separate treatment study is assessing the antibody MBP134, the antiviral remdesivir and a combination of the two in patients with confirmed Bundibugyo virus disease. The health organisation said another antibody, maftivimab, would soon be added. These are investigations into treatment, not proof that the medicines work against Bundibugyo.
For the vaccine candidates, the next steps are national approvals and their entry into the trial. The results will be needed to establish how well the products perform and whether they can offer a useful additional tool for future outbreak responses.
Featured image: AI-generated illustration.
