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).

WHO’s director-general, Tedros Adhanom Ghebreyesus, said in a social media post on Friday that 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.

Ervebo, a vaccine approved for use against the more common Zaire strain of Ebola, will be put through a full-scale human trial to see if it offers any cross-protection against the Bundibugyo species of Ebola that is behind the epidemic.

“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 WHO, in response, 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.

Vaccines in the pipeline

The so-called Tumaini trial is a single trial framework that can test the safety, efficacy and immunogenicity of multiple vaccines.

The trial will use a ring vaccination approach: immunising contacts deemed to be at high risk of infection.

The trial is set to incorporate two Bundibugyo-specific candidate vaccines, which are currently advancing through earlier-stage, smaller-scale clinical trials.

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 have received funding from the Coalition for Epidemic Preparedness Innovations and are expected to enter the trial “shortly”, CEPI said in a statement.

The trial will 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.