Labs race to develop Ebola vaccine for Bundibugyo strain outbreak in Central Africa

Late April brought word of a new Ebola outbreak in the Democratic Republic of Congo, and within weeks it had crossed borders into Uganda and South Sudan. The culprit was the Bundibugyo strain—a variant that had killed roughly 140 people and infected an estimated 1,000 more by late May. What made this outbreak particularly urgent was a simple, brutal fact: there were no approved vaccines or treatments for Bundibugyo, despite it being the third time this specific strain had sparked a major outbreak in Central Africa.

The World Health Organization and researchers around the world immediately understood what was at stake. Bundibugyo carries a fatality rate between 30 and 50 percent. Authorities believed the virus had begun spreading weeks earlier, possibly accelerated by a superspreader event—likely a funeral—in early May. The disease had found its way into one of the world's most difficult-to-reach regions, where flight cancellations and access problems were already hampering efforts to deliver tests and medical supplies to Ituri Province.

Within days, the race was on. Thomas Geisbert, a virologist who had helped develop Ervebo, the existing vaccine for the more common Zaire strain, had designed a single-shot vaccine candidate against Bundibugyo years earlier. His work, published in 2013, had languished in relative obscurity—a fate he knew well from his earlier research on what became Ervebo, which took more than a decade to move from lab to distribution. The problem was simple economics: pharmaceutical companies saw no profit in a vaccine for a rare African outbreak. "There have been no incentives for major pharmaceutical firms to get involved, because it is not profitable," Geisbert told the AFP.

But the outbreak had changed the calculus. Chinese researchers published a new study in the journal PNAS describing an mRNA vaccine—the technology that had proven itself during the Covid-19 pandemic—designed to protect against three major Ebola strains, including Bundibugyo. Oxford University researchers announced they were collaborating with the Serum Institute of India, the world's largest vaccine manufacturer, to accelerate production of a viral vector vaccine called ChAdOx1 BDBV. "We are working on logistics at full speed," said Teresa Lambe, head of vaccine immunology at the Oxford Vaccine Group, "but we cannot yet give a precise timeline."

The WHO's assessment was sobering but not hopeless. The most promising candidate—a vaccine using the same platform as existing Zaire-strain shots—would likely take six to nine months to develop, test in humans, and distribute. An alternative approach, using the same technology Oxford had employed for AstraZeneca's Covid vaccine, might be ready for human trials in two or three months, though significant uncertainties remained about its effectiveness in animals. A third candidate, VSV-BDBV, was still in academic research at the University of Texas but was expected to move toward large-scale production soon.

Yet obstacles remained formidable. The mRNA vaccines, while promising, were expensive to manufacture and required cold-chain storage—a serious limitation in Central Africa. Flight disruptions meant that even basic diagnostic tests were struggling to reach affected areas. An Imperial College London model suggested the actual number of cases might already exceed 1,000. Chikwe Ihekweazu, the WHO's emergency response chief, laid out the immediate priority: "Our absolute focus right now is identifying every existing transmission chain. That will allow us to define the true scale of the outbreak and deliver the care that is needed."

Bundibugyo itself was relatively new to science. It had first been identified in 2007 when a mysterious illness emerged in Uganda's Bundibugyo District, near the Congo border. Another outbreak struck the Democratic Republic of Congo in 2012. This was only the third time the strain had sparked a major crisis. The laboratories racing to develop a vaccine were working against a clock that measured not just months but lives—and they knew that even if they succeeded, getting doses to the people who needed them most would be a challenge as difficult as the science itself.