Key Points
- The World Health Organization (WHO) has recommended two additional Ebola vaccine candidates for clinical evaluation in the Democratic Republic of the Congo (DRC).
- The vaccines, ChAdOx1 and Moderna’s mRNA-1469, were specifically developed to target the Bundibugyo virus.
- The vaccines will be evaluated through the WHO-supported Tumaini trial, subject to national approvals.
- The WHO-sponsored PARTNERS trial is also assessing potential treatments, including monoclonal antibodies and antiviral drugs.
- Initial treatment trial findings are expected in the coming months, while vaccine trial results are anticipated in early 2027.
Main Story
The World Health Organization (WHO) has recommended two additional Ebola vaccine candidates for clinical evaluation in the Democratic Republic of the Congo (DRC), marking another important step in efforts to strengthen the response to the ongoing Bundibugyo virus outbreak.
The two vaccine candidates, ChAdOx1 and Moderna’s mRNA-1469, were specifically developed to target the Bundibugyo virus, a strain of Ebola for which there is currently no approved vaccine.
In a statement issued on Wednesday, WHO said the vaccines would be evaluated for the first time during an outbreak of the disease, providing researchers with an opportunity to gather evidence about their safety and effectiveness under real outbreak conditions.
ChAdOx1 was developed by the University of Oxford in partnership with the Serum Institute of India, while mRNA-1469 was developed by Moderna.
The organisation explained that its independent Technical Advisory Group on Candidate Vaccine Prioritisation recommended both candidates after reviewing available preclinical and early clinical evidence. However, their inclusion in the outbreak vaccination programme remains subject to approval by the relevant national authorities.
WHO Director-General, Dr Tedros Ghebreyesus, described the development as an example of what international scientific collaboration could achieve during a public health emergency.
He thanked researchers, healthcare workers, international partners and clinical trial participants for their contributions, noting that the evidence generated through the studies could help save lives.
Tedros, however, cautioned that vaccines alone would not bring the outbreak to an end, stressing that they must complement other public health measures.
The Institut National de Recherche Biomédicale (INRB), the DRC’s national public health and biomedical research institute, is leading the vaccine research with support from WHO, the University of Antwerp and other international partners.
Other organisations involved include Epicentre, Médecins Sans Frontières (MSF), the Institute of Tropical Medicine of Antwerp and the Africa Centres for Disease Control and Prevention.
According to WHO, investments from the Coalition for Epidemic Preparedness Innovations (CEPI) helped accelerate the development of the vaccine candidates.
The clinical evaluation is being conducted through the Tumaini trial, which is designed to assess multiple vaccine candidates using a ring-vaccination approach.
Under this strategy, people who have had contact with confirmed Ebola patients, as well as their contacts, are identified and offered vaccination. The approach is intended to create protective barriers around infected individuals and reduce further transmission.
The strategy builds on experience from the 2014–2016 West African Ebola outbreak. During that outbreak, a landmark clinical trial in Guinea established the effectiveness of Ervebo against the Zaire ebolavirus strain.
Ervebo is also the first vaccine being evaluated in the current Tumaini trial to determine whether it provides protection against the Bundibugyo virus.
Tedros disclosed that four vaccination rings had already been established, with preparations ongoing to create additional rings involving people who had come into contact with individuals who became ill or died from the disease.
The Issues
The development of vaccines against Bundibugyo virus is particularly important because Ebola is not caused by a single virus strain.
While vaccines have been developed against the Zaire ebolavirus, their effectiveness cannot automatically be assumed against other Ebola species, including Bundibugyo.
This creates a significant challenge for outbreak response, as health authorities may have limited medical tools available when a different strain emerges.
The absence of an approved vaccine specifically targeting Bundibugyo means that researchers must gather reliable evidence before any candidate can be considered for wider use.
The current outbreak therefore highlights the need for continued investment in vaccine development, rapid clinical research and stronger disease surveillance systems.
What’s Being Said
Beyond vaccine development, WHO says research into potential treatments is also progressing through its sponsored PARTNERS trial, which was launched in July.
The trial is evaluating whether monoclonal antibody MBP134, the antiviral drug remdesivir or a combination of both can improve survival among patients with confirmed Bundibugyo virus disease.
According to Tedros, another treatment candidate, maftivimab, will soon be introduced into the study.
A separate but related investigation is also examining obeldevisir as a possible option for preventing infection among people exposed to the virus.
These studies are expected to provide important information about treatment options for patients, particularly those who become infected during outbreaks.
What’s Next
WHO said it would continue supporting the research through its Research and Development Blueprint and Health Emergencies Programme.
Its support includes providing technical guidance, developing research protocols, coordinating international partners and ensuring that clinical studies meet established scientific and ethical standards.
The organisation also confirmed that initial findings from the treatment trials are expected in the coming months.
Meanwhile, results from the vaccine trial are anticipated in early 2027, although the introduction of additional candidates will depend on national approvals and trial requirements.
Bottom Line
WHO’s recommendation of two additional Ebola vaccine candidates represents meaningful progress in the fight against the Bundibugyo virus.
However, the real test will be whether these vaccines can demonstrate sufficient safety and effectiveness during the ongoing outbreak.
With treatment trials also underway, the research offers hope of expanding the medical options available to patients and health authorities.
For the DRC and other countries at risk of Ebola outbreaks, the findings could help strengthen future preparedness and improve the global response to one of the world’s most dangerous infectious diseases.
