WHO restricts Ervebo use in Bundibugyo outbreak

The World Health Organisation (WHO) has issued new emergency guidance on using the licensed Ervebo vaccine during outbreaks of Bundibugyo virus disease, now limiting its use to research protocols.

The organisation made this known in a statement on Tuesday, saying the guidance followed an extraordinary meeting of the Strategic Advisory Group of Experts on Immunisation held on 19 August, 2026.

WHO said Ervebo should currently be used against Bundibugyo virus only within a research protocol to generate evidence on its effectiveness, rather than through broader routine outbreak vaccination.

According to the organisation, a ring vaccination randomised controlled trial would be the most robust approach for determining Ervebo’s efficacy against Bundibugyo virus disease among affected populations.

The organisation said broader vaccine use before trial results would require a comprehensive risk-mitigation plan addressing potential risks associated with such use during outbreak response and monitoring recipient health outcomes promptly.

“WHO continues recommending preventive Ervebo vaccination for healthcare and frontline workers in Ebola virus priority areas with previous Ebola disease outbreaks.”

The organisation in its guidance, also emphasised preventive vaccination policy.

“In areas affected by the current Bundibugyo outbreak, Ervebo should only support outbreak response through research protocols, including ring trials or observational vaccine-effectiveness studies.” WHO said, stressing that evidence generation remains essential.

“Such studies could provide additional evidence about the potential performance of Ervebo against Bundibugyo virus during ongoing outbreaks,” it said.

The statement said those findings could inform future policy and vaccine recommendations later.

The organisation said off-label use might exceptionally be considered where research was not feasible, provided reliable vaccination records could track recipients and subsequent health outcomes over time and support safety monitoring.

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It urged accelerated development and rigorous evaluation of vaccines specifically targeting Bundibugyo virus disease and post-exposure prophylaxis products for outbreak preparedness and response, and other needed countermeasures for affected populations globally.

The organisation also called for stronger coordination among partners supporting the Democratic Republic of the Congo (DRC) and other countries considering Ervebo within research protocols to ensure consistent implementation and evidence sharing promptly.

It recommended developing and sharing master protocols for ring vaccination trials and high-quality observational studies to ensure timely, coordinated evidence generation during the outbreak and future emergency responses in affected countries.