A new virus, an old promise
When the ministries of health in the Democratic Republic of the Congo and Uganda declared an Ebola outbreak on 15 May 2026, the genomics told an uncomfortable story. The pathogen was not the Zaire ebolavirus we have spent a decade learning to fight, but Bundibugyo virus, a species responsible for only two prior outbreaks, the last in DRC in 2012. There is no licensed vaccine for it, and when this epidemic began, there was not a single Bundibugyo candidate in clinical development.
That is the gap the Coalition for Epidemic Preparedness Innovations (CEPI) built its "100 Days Mission" to close. After COVID-19, CEPI committed to a world that could move from identifying a novel threat to a safe, effective vaccine within 100 days of identifying the pathogen. This outbreak is the closest that promise has ever come to a real-world stress test. So it is worth asking plainly: will they make it?
The clock, and the honest answer
The mission's clock started when the World Health Organization declared a Public Health Emergency of International Concern on 17 May. Africa CDC followed with a Public Health Emergency of Continental Security on 18 May. Counting from that Day 0, the 100-day mark falls around 25 August 2026.
The literal target, a deployed vaccine controlling this outbreak, will not be met, and it was never the realistic yardstick. You cannot license, manufacture and ring-vaccinate against a virus in three months when you are starting from preclinical candidates rather than a shelf-ready product. The independent assessment of the response said as much within the first fortnight: none of the candidates are yet in clinical-grade form, and no Bundibugyo-specific vaccine is expected for near-term deployment in this outbreak.
But that is the wrong way to score the mission, and CEPI knows it. The honest metric is process speed: whether pre-validated platforms can be pushed into first-in-human trials, and toward emergency ring use, faster than ever before. On that measure, something genuinely unprecedented is under way, and it deserves to be judged on its own terms rather than against a slogan.
What is actually on the table
Within roughly two weeks of Day 0, CEPI moved. On 1 June it announced it would urgently accelerate three investigational Bundibugyo vaccines, candidates from IAVI, Moderna, and the University of Oxford, with the Oxford candidate to be manufactured at the Serum Institute of India. The three span complementary platforms: a recombinant VSV viral vector (the same backbone as the licensed Zaire vaccine, Ervebo), an mRNA approach, and a third platform with prior data against related filoviruses.
Crucially, none of this started from a blank page. In January 2026, months before the spillover, CEPI had already committed US$26.7 million, alongside the EU's Horizon Europe programme, for Oxford and partners to develop multivalent vaccines covering Ebola, Sudan, Bundibugyo and Marburg viruses. That foresight is the only reason a Bundibugyo candidate exists to accelerate at all. It is the quiet, unglamorous case for sustained preparedness funding, made vivid.
The money has since followed the emergency. CEPI awarded Public Health Vaccines US$1.9 million for an rVSV-based candidate that gave full protection against lethal challenge in non-human primates, and 83% protection post-exposure, in early studies, and opened a call for proposals running to 22 June with explicit priority for Africa-based groups. The University of Oxford, through the Oxford Vaccine Group, is advancing its candidate toward trials with the Serum Institute of India providing manufacturing and a commitment to affordable access for affected countries. On 12 June, the US Department of State committed US$50 million to CEPI to fast-track countermeasures. And the Gates Foundation unlocked US$15 million in emergency funding, structured as three equal tranches for velocity, with US$5 million directed to Africa CDC for regional coordination and cross-border surveillance.
The response beyond the vaccine
A vaccine, however fast, will not be what brings this outbreak under control. That work belongs to the public-health machinery, and to therapeutics already in trials.
Africa CDC and WHO launched a joint continental preparedness and response plan on 5 June, seeking US$518 million to help African countries detect and respond, reinforced by contributions such as South Africa's US$2.5 million through the Africa CDC Epidemics Fund. The Gates Foundation has tied its support to the Joint Emergency Action Plan between Africa CDC and WHO AFRO, precisely to avoid the fragmented, parallel responses that have hampered past emergencies.
On treatment, WHO convened its International Health Regulations Emergency Committee and, acting on advisory-group recommendations, is supporting DRC and Uganda to run a clinical trial: the broadly neutralising antibody MBP134 and REGN3479 for treatment, and the oral antiviral obeldesivir for post-exposure prophylaxis. None of this would stand up so quickly without infrastructure built in calmer times, including the ISARIC PARTNERS adaptive trial platform co-developed with WHO, now doing exactly the job it was designed for.
This is the part of the story that matters most for the outbreak's trajectory. Modelling from the US CDC found that the single biggest lever is the proportion of patients successfully isolated: with around 70% entering isolation, scenarios producing more than 10,000 cases became rare. Isolation, safe burials and contact tracing, not a new vaccine, will decide whether this is contained.
Why this outbreak is harder than the last
By mid-June, DRC had reported 837 confirmed cases and 196 confirmed deaths, with Ituri province bearing the brunt across twenty health zones; Uganda had recorded 19 confirmed cases and two deaths from imported infection. CEPI has called it already the third-worst Ebola outbreak in history, with confirmed cases doubling in a recent ten-day span, though part of that surge reflects a long-overdue scale-up in testing finally catching up with reality.
Two features make this episode especially dangerous. The first is context: the outbreak sits in a landscape of armed conflict, displacement and mining-driven population movement, where contact follow-up is weak and several listed contacts have died before they could be isolated. The second is biology. Genomic evidence points to a novel zoonotic spillover of a distinct Bundibugyo lineage, not a chain traceable to a previous outbreak.
That distinction matters, and it is where commentary often goes wrong. Filoviruses persist between outbreaks through two very different routes. One is maintenance in an animal reservoir, very probably bats, where the virus can circulate without obvious disease until conditions favour spillover into a naive human population. The other is persistence in human survivors: we now have close to ten documented Ebola flare-ups, all Zaire ebolavirus, in which the virus re-emerged from a recovered individual months or years later. Both routes help explain why Ebola does not simply burn out and vanish, a question made urgent by the tens of thousands who survived the 2013 to 2016 West African epidemic. But the survivor-reactivation mechanism is a Zaire story, and it is not the origin of this Bundibugyo outbreak. This one came from the reservoir, fresh.
So, will they meet it?
No, if "meeting the 100 Days Mission" means a Bundibugyo vaccine in arms stopping this outbreak by late August. Yes, in the only sense that is achievable and honest: candidates built on pre-validated platforms are moving toward first-in-human trials at a pace that would have been impossible a decade ago, financed and coordinated within weeks of Day 0.
The real verdict will not be a binary. It will be measured in how many days are shaved off the path to a trial-ready, then deployment-ready, vaccine, and in whether the preparedness investments that made any of this possible are sustained rather than summoned, again, only in crisis. The communities of Ituri and Kampala may not be protected by these vaccines in time. The next ones might be. That, in the end, is what the mission was always for.
Sources: WHO Disease Outbreak News (DON602, DON603, DON607); WHO and Africa CDC continental response plan; US CDC MMWR Early Release reports and HAN advisory, June 2026; CEPI announcements, January to June 2026; University of Oxford; Gates Foundation; ECDC outbreak page; IPPS Day 0 and Day 15 statements. Figures as of mid-June 2026 and subject to revision as case classification continues.