WHO Recommends Two Additional Vaccine Candidates for Ebola Trial

The proposed additions target Bundibugyo virus and still require national approval before trial entry.

WHO-convened experts have recommended adding two vaccine candidates to the Tumaini trial in the Democratic Republic of the Congo. In a November 4 release, the organisation said the candidates are designed to protect against Bundibugyo virus, which is responsible for the outbreak under study.

The products are ChAdOx1, developed by the University of Oxford with the Serum Institute of India, and Moderna’s mRNA-1469. WHO said its advisory group recommended further evaluation after reviewing preclinical and early clinical evidence. Entry into the trial will follow the necessary national approvals.

The study uses a ring-vaccination approach involving contacts of confirmed cases and can evaluate multiple candidates within a single trial. WHO also described related treatment research and said vaccine trial results were expected in early 2027. The recommendation is not a declaration that either candidate is proven effective against the outbreak virus or approved for routine use.

Context: A clinical trial is intended to answer questions that available evidence cannot yet settle. Promising laboratory findings or early studies do not replace evidence about protection and safety in the population and setting being studied. Clear distinctions between candidate, trial participant and authorised product are therefore important.

The next developments will include approval decisions, trial progress and the eventual release of results. Those findings will need to be assessed in relation to the study design and the number of events observed. The announcement represents an expansion of research options during an outbreak, with any claim about the candidates’ public health role dependent on evidence that the trial has yet to generate.