Scientists at Oxford University are developing a vaccine against a rare and lethal strain of Ebola, with researchers saying doses could be ready for clinical trials within two to three months if animal testing produces encouraging results.
The urgency stems from an outbreak in the Democratic Republic of Congo that has produced 750 suspected cases and 177 deaths. The strain responsible, known as Bundibugyo, kills roughly one in three of those it infects. No approved vaccine exists for it. On Sunday, the World Health Organization declared a public health emergency of international concern, and has since upgraded its risk assessment for the DRC from high to very high. Across the wider region the risk is also now considered high, though globally it remains low. The WHO has been explicit that the outbreak does not constitute a pandemic.
Bundibugyo is rare. It has caused only two previous outbreaks, in Uganda in 2007 and the DRC in 2012, and had not been seen for more than a decade before the current emergency. This gap in its history is partly why no vaccine was developed sooner, and why researchers are now working against an uncertain timeline.
The Oxford team is using a platform called ChAdOx1, which was originally developed for their Covid-19 vaccine. The technology works by taking a common cold virus that normally infects chimpanzees and engineering it so that it can be safely introduced into humans. That modified virus is then used to carry genetic material from the Bundibugyo strain into human cells. The immune system learns to recognise the virus from this material without the patient ever being exposed to Ebola itself. For the current vaccine, the team has loaded the platform with genetic code specific to Bundibugyo, following the same principle used during the pandemic with the Covid virus.
Animal testing is now under way in Oxford. Whether those results will support moving into human trials remains to be seen. The WHO has noted that no animal data currently exists to confirm the vaccine's effectiveness, and has said its readiness for clinical trials will depend on what that testing shows. A separate experimental Bundibugyo vaccine is being developed elsewhere, but is not expected to reach trial stage for six to nine months, making the Oxford timeline considerably faster if the science holds.
Professor Katie Lambe, Calleva Head of Vaccine Immunology at the Oxford Vaccine Group, said the Serum Institute of India was already lined up to manufacture doses at scale once Oxford could supply the necessary medical-grade material. "Once we get starting material to them they can go fast and they can go big," she told the BBC. She added that speed was a priority given the trajectory of the outbreak, while also noting that contact tracing and quarantine might yet be sufficient to bring it under control.
If the vaccine does prove effective and is eventually deployed, it will not be used in the same way as a mass vaccination programme. Ebola vaccines are administered through ring vaccination, a targeted approach in which immunisation is offered to the close contacts of confirmed cases and to healthcare workers treating infected patients. Given how infectious Ebola patients can be, healthcare staff are considered a particular priority.
The current outbreak highlights a broader gap in preparedness. While a vaccine exists for the Zaire strain, the most common cause of large Ebola outbreaks, no equivalent has been developed for Bundibugyo or the Sudan strain. The Oxford team had previously worked on vaccines for both the Sudan strain and the related Marburg virus, giving them relevant experience to draw on as they move quickly on Bundibugyo.
Whether the next few months produce a viable candidate will depend on the animal data. If it is promising, the world may have a new tool available at a point when the outbreak could still be contained. If it is not, the work will at least have advanced the science for future reference.
