Africa CDC prepares Ervebo vaccine trial against Bundibugyo Ebola in DRC

The Africa Centres for Disease Control and Prevention and international partners are organizing a clinical trial to test whether Merck's ↗ 1.50% licensed Ervebo vaccine can protect frontline health workers against the Bundibugyo strain of Ebola in the Democratic Republic of Congo, according to a Bloomberg report published on Monday. The trial could begin within two weeks of receiving ethical and regulatory approvals.nampa+1

A Vaccine Without Proof

Ervebo is the only licensed Ebola vaccine in the world, but it was developed and approved specifically for the Zaire strain — the species responsible for the devastating 2014–16 West African epidemic. Its efficacy against Bundibugyo virus remains unproven in humans. The WHO in May recommended that Ervebo "should not be used outside carefully designed research settings" during the current outbreak, to allow its performance against Bundibugyo virus disease to be properly assessed.who+1

Thomas Geisbert, a filovirus researcher at the University of Texas Medical Branch, told Nature in May that Ervebo's chances against Bundibugyo were uncertain. "It's kind of a coin flip," he said, estimating the vaccine might be roughly 50% effective.nature

Outbreak Context

The DRC's 17th Ebola outbreak, declared on May 17, has become the largest Bundibugyo outbreak on record. As of early July, WHO reported more than 1,460 confirmed cases in the DRC and 20 in Uganda, with at least 454 deaths — a case fatality ratio of about 31%. The outbreak is centered in Ituri province in the northeast, with cases also confirmed in France.afro.who+2

A separate treatment trial — the WHO-sponsored PARTNERS study — enrolled its first patient on July 2 at the Evangelical Medical Center in Bunia, testing Mapp Biopharmaceutical's monoclonal antibody MBP134 and Gilead Sciences's ↘ 2.20% remdesivir against optimized supportive care. Meanwhile, Oxford University began the world's first human trial of a Bundibugyo-specific vaccine candidate, ChAdOx1 BDBV, on July 13, enrolling 50 healthy adults in an early-stage safety study.who+3

Race Against Time

The planned Ervebo trial represents a parallel track — aiming to determine whether an existing, mass-produced vaccine already in global stockpiles might offer some cross-protection for the health workers most at risk. The WHO's May expert panel had identified a purpose-built rVSV Bundibugyo vaccine, developed by the International AIDS Vaccine Initiative, as the most promising candidate, but estimated it would take seven to nine months before clinical testing could begin.who

With the outbreak still growing and no approved countermeasures in hand, the Africa CDC's push to fast-track the Ervebo study reflects a calculation that even partial protection could save lives on the front lines while strain-specific vaccines work through development pipelines.