Bundibugyo Ebola passed 2,000 deaths in 86 days, and the one licensed vaccine does not target it

The Bundibugyo virus outbreak declared in the Democratic Republic of the Congo on 15 May 2026 had produced 4,381 confirmed cases and 2,011 confirmed deaths by 9 August, according to the World Health Organization's thirteenth weekly external situation report. That is a case fatality ratio of 45.9 per cent. In the week covered by the report alone, 579 confirmed cases and 304 confirmed deaths were added. Ituri province accounts for 85.8 per cent of cumulative cases and 80.6 per cent of deaths, so the outbreak is centred there but is no longer confined to it, and cases have also been reported in Uganda.

By 12 August, when STAT reported on trial planning, the count had passed 4,500 confirmed cases and 2,060 deaths. WHO director-general Tedros Adhanom Ghebreyesus said it was "already the second-biggest Ebola epidemic on record, and it's moving faster than any previous Ebola outbreak". A month earlier, on 13 July, Nicole Lurie of the Coalition for Epidemic Preparedness Innovations had described it as the third largest. Both statements were accurate when made, which is the clearest indicator of the trajectory.

The widely repeated framing that WHO is abandoning ring vaccination understates the problem. There is no ring vaccination campaign to abandon, because there is no vaccine licensed against this species. Merck's Ervebo is licensed against Ebola virus, species Orthoebolavirus zairense, not Bundibugyo. In emergency guidance issued on 28 May 2026, WHO said evidence of cross protection against Bundibugyo is "very limited and insufficient", advised against programmatic deployment of Ervebo for this outbreak, and said the vaccine should not be used outside carefully designed research settings. Control has therefore rested on surveillance, contact tracing, infection prevention and community engagement.

That is what the trial under negotiation would change. STAT reported on 12 August that WHO is working towards a multi armed phase 3 study that individually randomises known contacts to vaccine or placebo, rather than the ring design used in the 2015 trial that supported Ervebo's licensure. Vasee Moorthy, who leads WHO's R&D Blueprint work, is among those involved. The protocol had not yet been submitted to Congolese regulatory and ethics committees at the time of that report. A WHO technical advisory group meeting on 31 July recommended that Ervebo be prioritised for inclusion in a randomised trial on the basis of preliminary animal data suggesting some cross protection against death, while stating that a vaccine developed specifically against Bundibugyo remains the preferred option. The International Coordinating Group on Vaccine Provision controls a stockpile of about 500,000 Ervebo doses.

Work on species specific vaccines is further along than it usually is this early in an outbreak. On 13 July the University of Oxford's Oxford Vaccine Group opened BD-Ebov, described as the world's first phase 1 trial of a Bundibugyo vaccine, testing ChAdOx1 BDBV in 50 healthy adults aged 18 to 55. The Serum Institute of India manufactured about 620,000 doses in two weeks and supplied 4,000 investigational doses for the trial, under a CEPI programme worth USD 8.6 million. Teresa Lambe, the study's lead scientific investigator, noted that the milestone came 57 days after WHO declared the outbreak a public health emergency of international concern, which places that declaration on 17 May 2026. UN News has given the date as 16 May. A second phase 1 trial, of a Moderna messenger RNA candidate, was launching in Canada in early August. Results from the phase 1 studies are expected around September 2026. A post exposure prophylaxis trial of an oral antiviral, given for 10 days, was already running in Ituri with more than 25 participants enrolled by early August.

The damage is not only in the case counts. UNICEF reported that more than 300 children had died by 7 August; children make up close to a quarter of confirmed cases but about a third of deaths. UN deputy spokesperson Farhan Haq said use of health services in the hardest hit areas had fallen by more than 40 per cent as fear of infection kept people away, and WHO has reported that maternal deaths in Ituri have nearly doubled since the outbreak began. Close to a million people in the province were already displaced by conflict. On 14 August, WHO convened the Central African Republic, the Democratic Republic of the Congo, the Republic of the Congo, South Sudan and Uganda in Bangui to agree cross border surveillance measures.

What is unresolved is whether the placebo controlled design survives review. The trial protocol has not been published, the Congolese regulator and ethics committees have not ruled on it, and no source has said what would happen to the placebo arm if a Bundibugyo specific vaccine clears phase 1 in September while the trial is still enrolling.