GENEVA — The first clinical trial of an Ebola vaccine in the outbreak gripping the Democratic Republic of Congo began Friday, the head of the World Health Organization said.

The DR Congo’s worst-ever Ebola outbreak has passed the 9,700-case mark, with the number of deaths exceeding 4,600.

Among the many challenges facing the response is the lack of any approved vaccines or treatments for the Bundibugyo species of Ebola behind the epidemic.

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

The trial began with the first shot of Ervebo being administered in Bunia, the capital of the DRC’s northeastern Ituri province, which is the epicentre of the outbreak.

“Science gives us hope. Today, in Bunia DRC, the first participants were vaccinated in a new Ebola vaccine trial called Tumaini, which means ‘hope’ in Swahili,” WHO chief Tedros Adhanom Ghebreyesus said on X.

“This trial will help us understand whether any of the vaccine candidates designed for Bundibugyo virus work,” he said, adding that in the meantime, the existing Ervebo vaccine would be tested.

“WHO is supporting this DRC-led effort to find answers and save lives.”