WHO Begins First Ebola Vaccine Clinical Trial in DR Congo Outbreak

The World Health Organization (WHO) has announced the beginning of the first clinical trial of an Ebola vaccine in the outbreak that started in the Democratic Republic of Congo (DRC). The agency's director-general, Tedros Adhanom Ghebreyesus, shared the news in a social media post on Friday.

Tedros said participants in the trial were vaccinated with the Ervebo vaccine in Bunia, the capital of the DRC's northeastern Ituri province, which is the epicentre of the Ebola outbreak — meaning the testing of the vaccine has begun exactly where infections are concentrated.

Ervebo is a vaccine approved for use against the more common Zaire strain of Ebola. The epidemic this time, however, is being driven by the Bundibugyo species, so the vaccine will be put through a full-scale human trial to see if it offers any cross-protection against Bundibugyo.

"This trial will help us understand whether any of the vaccine candidates designed for Bundibugyo virus work," the WHO chief said on X. "WHO is supporting this DRC-led effort to find answers and save lives," he added.

The DRC declared its 17th and worst-ever Ebola outbreak in May and has since reported more than 9,700 cases, with the number of deaths exceeding 4,600. The figures alone show this outbreak has surpassed all previous records in the country.

In response to the scale of the crisis, the WHO triggered a public health emergency of international concern, its second-highest alert level.

The current outbreak has now been reported in four countries across eastern, central and western Africa, giving it the widest geographic spread of any Ebola outbreak on the continent to date.

The so-called Tumaini trial is a single trial framework that can test the safety, efficacy and immunogenicity of multiple vaccines at once, allowing results for several candidates to emerge under one umbrella instead of through separate trials.

The trial will use a ring vaccination approach: immunising contacts deemed to be at high risk of infection, building a protective ring around the outbreak's chains of transmission.

Two Bundibugyo-specific candidate vaccines, currently advancing through earlier-stage, smaller-scale clinical trials, are set to join the trial. One is a ChAdOx1 adenoviral vector jab being developed by the University of Oxford; the other, by the US-based Moderna group, uses mRNA technology.

Both candidates have received funding from the Coalition for Epidemic Preparedness Innovations, and CEPI said in a statement that they are expected to enter the trial "shortly".

The trial will also include pregnant women and children aged 12 years and older, generating evidence for populations that are often excluded from clinical trials.

WHO emergencies director Chikwe Ihekweazu said the trial was set up to generate the rigorous evidence needed to determine whether the participating vaccines could protect people at risk. The strategy for fighting an outbreak now spread across four countries will depend on that evidence.