Two Ebola vaccine candidates target a gap in outbreak defence
GENEVA — World Health Organization advisers have recommended two experimental vaccines for testing against Bundibugyo virus, the cause of the current Ebola outbreak in the Democratic Republic of the Congo. The candidates specifically target a virus for which protection from the existing Ervebo vaccine remains unproven in humans.
The candidates are ChAdOx1, developed by the University of Oxford with the Serum Institute of India, and Moderna’s mRNA-1469. They are recommended for inclusion in the ongoing Tumaini clinical trial, subject to national approvals. The recommendation permits further evaluation and does not establish that either vaccine prevents disease.
WHO said its independent advisory group assessed available preclinical and early clinical evidence before recommending the candidates. Their inclusion would mark the first time vaccines specifically designed against Bundibugyo virus are evaluated during an outbreak.
The DRC’s Institut National de Recherche Biomédicale is leading Tumaini, which tests multiple candidates through a ring-vaccination approach involving contacts of confirmed cases. Ervebo is already being evaluated through the trial, and WHO said four vaccination rings had been established, with more being prepared. Vaccine results are expected in early 2027.
Ervebo’s established use against Ebola virus, also known as Zaire ebolavirus, cannot automatically be extended to Bundibugyo. WHO guidance says laboratory and animal findings suggest possible protection, but the evidence remains insufficient to determine whether it provides meaningful protection against Bundibugyo disease in people. The agency recommends its use against this virus within research protocols.
The outbreak was declared in May in the DRC’s northeastern Ituri province and designated a public health emergency of international concern. The response includes surveillance, laboratory testing, contact tracing, infection prevention and patient care, supported by WHO and international partners.
For affected communities, the trials offer a route towards evidence on additional protection while established containment work continues. WHO’s guidance stresses that vaccine research must accompany proven outbreak-control measures and clear communication about what protection remains unknown.
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