Ebola vaccine trial begins in DR Congo's worst outbreak

The Democratic Republic of Congo's Ebola outbreak is its worst ever. It has passed 9,700 cases and more than 4,600 deaths. No vaccine is approved for the Bundibugyo strain driving it. On Friday, the first shot of Ervebo, a vaccine approved for the Zaire strain, was given in Bunia, the capital of Ituri province and the centre of the outbreak. The Tumaini trial, led by the DRC with WHO support, is testing whether the shot offers any cross-protection. WHO chief Tedros Adhanom Ghebreyesus said the "first participants were vaccinated in a new Ebola vaccine trial called Tumaini, which means 'hope' in Swahili."

Trial design and vaccine candidates

Tumaini is a single-framework trial that can test several vaccine candidates for safety, efficacy and immune response. It uses ring vaccination, immunizing contacts judged to be at high risk of infection. Two Bundibugyo-specific candidates are expected to join soon. They are now in earlier, smaller trials: a ChAdOx1 adenoviral-vector shot from the University of Oxford and an mRNA vaccine from Moderna. Both have received funding from the Coalition for Epidemic Preparedness Innovations and are expected to enter the trial "shortly." The study will also enrol pregnant women and children aged 12 and older, groups that are often left out of vaccine trials.

If the vaccines work, this would be the first clear evidence of protection against Bundibugyo, a major advance that could change how responders handle this outbreak and future ones. WHO emergencies director Chikwe Ihekweazu said a successful trial would provide the rigorous evidence needed to show whether the vaccines can protect people at risk. Steve Ahuka-Mundeke, the DRC Ebola response incident manager, said bringing the trial into the response is "an important step toward addressing the urgent needs of affected communities."

Significance and outbreak context

The DRC declared its 17th Ebola outbreak on 15 May. Two days later, WHO triggered a public health emergency of international concern, its second-highest alert level. Ebola spreads through contact with bodily fluids and causes a hemorrhagic fever. It has killed more than 15,000 people in Africa over the past 50 years.