Deadly Ebola Gap Spurs Vaccine Sprint

Scientists in protective gear working with a syringe in a laboratory — Photo: Sirichai Saengcharnchai / Shutterstock

A rare Ebola strain with no approved vaccine has pushed global health experts to fast‑track a new “most promising” shot from a Singapore lab.

Story Snapshot

Experts convened by the World Health Organization (WHO) say a single‑dose rVSV Bundibugyo shot is the most promising vaccine candidate against the current Bundibugyo Ebola outbreak.
Singapore‑based Hilleman Laboratories will develop and manufacture doses so the vaccine can move into human clinical trials within months.
The Bundibugyo strain driving the epidemic in Congo and Uganda has no licensed vaccine or specific treatment, leaving only classic outbreak control tools.
The rVSV platform behind the new shot is the same proven technology used in Merck’s successful Ervebo Ebola vaccine.

WHO backs single-dose rVSV Bundibugyo vaccine as top candidate

World Health Organization experts met in late May and reviewed all known Bundibugyo Ebola vaccine options. They judged a single-dose rVSV Bundibugyo vaccine as the most promising candidate to prevent disease from this rare strain. The shot was originally developed by the International AIDS Vaccine Initiative, a nonprofit that works on global health threats. Experts said this one-dose vaccine will likely need about seven to nine months of work before it is ready to be tested in human clinical trials.

The Bundibugyo outbreak in the Democratic Republic of the Congo and Uganda is one of the largest Ebola emergencies ever recorded, with thousands of suspected and confirmed cases and hundreds of deaths. Health officials say there is no licensed vaccine or specific treatment that targets Bundibugyo virus today. This gap forces doctors to rely on basic public health tools like rapid case finding, isolation, contact tracing, and safe burials, while they wait for better medical countermeasures.

Singapore’s Hilleman Laboratories steps in to make trial doses

On July 30, the Coalition for Epidemic Preparedness Innovations (CEPI) announced a partnership with Hilleman Laboratories in Singapore to turn the rVSV Bundibugyo design into real vaccine doses for trials. CEPI will provide up to 8.5 million U.S. dollars so Hilleman can refine the manufacturing process and produce clinical supplies at its new vaccine plant. Hilleman will start from rVSV Bundibugyo vaccine material created by the International AIDS Vaccine Initiative and may later support other rVSV-based shots.

Hilleman Laboratories is a joint venture between pharmaceutical company Merck Sharp & Dohme (MSD) and the Wellcome Trust, a large United Kingdom health charity. MSD developed Ervebo, the first approved Ebola vaccine for the Zaire strain, and will advise Hilleman on the rVSV technology platform. This gives the Bundibugyo project access to hard-won expertise from earlier Ebola work, including how to scale production and manage safety. The goal is a reliable, low‑cost vaccine that poorer countries can actually use when outbreaks hit.

Why rVSV technology matters in the Bundibugyo fight

The rVSV platform uses a weakened vesicular stomatitis virus that has been altered to carry Ebola surface proteins instead of its own. Past studies showed that a single shot of blended rVSV vaccines could fully protect non‑human primates against Marburg virus and three different Ebola species, including Bundibugyo. Merck’s rVSV‑ZEBOV version for the Zaire strain later demonstrated strong protection, with around 90 to 95 percent efficacy in trials, and became the Ervebo vaccine used in prior outbreaks.

🇺🇬 Uganda declares end to Ebola outbreak after 42 days with no new cases

Uganda has declared itself free of Ebola after going 42 days without a new infection, Health Minister Chris Baryomunsi announced Tuesday at a press conference in Kampala.

The outbreak infected 20 people… https://t.co/LYhnneMl40

— Drop Site (@DropSiteNews) July 28, 2026

Doctors stress that today’s approved Ebola vaccines do not cover Bundibugyo virus. Shots like rVSV‑ZEBOV and Ad26.ZEBOV/MVA‑BN‑Filo either target only the Zaire Ebola strain or have not proven protection against Bundibugyo in people. That means the world must build a strain‑specific solution. The World Health Organization and Africa Centers for Disease Control and Prevention have both called for urgent work on Bundibugyo vaccines, treatments, and better diagnostics to close this dangerous gap.

Other Bundibugyo candidates and the road ahead

While the one‑dose rVSV Bundibugyo shot sits at the top of the expert list, it is not the only vaccine in development. A ChAdOx1 Bundibugyo vaccine from Oxford University and the Serum Institute of India could be ready for human efficacy trials within two to three months, though experts still rank it second. Private groups like Public Health Vaccines are also working on rVSV Bundibugyo designs similar to Ervebo, expanding the pipeline in case the leading candidate runs into delays.

Researchers caution that “most promising” does not mean “proven.” The label reflects animal data, past success of rVSV technology, and expert judgment, not completed human trials. For now, Bundibugyo Ebola control still depends on classic outbreak tools and strong local health systems. If the Singapore‑led rVSV Bundibugyo shot passes safety and effectiveness tests, it could become the first licensed vaccine for this strain and a key part of global preparedness the next time this deadly virus appears.