The Bundibugyo variant is driving the Democratic Republic of Congo’s largest outbreak on record.
On Friday, the World Health Organization (WHO) recommended that the Ervebo vaccine be prioritized for human clinical trials in an effort to respond to the current Ebola virus outbreak in the Democratic Republic of Congo (DRC), which has infected more than 4,000 people.
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The recommendation comes after the WHO’s technical advisory group on vaccines met on July 31 to analyze the different candidates, concluding that animal studies show Ervebo, manufactured by U.S. pharmaceutical company Merck, provides “some level of protection.”
In trials involving primates, survival rates of up to 75% were achieved among vaccinated subjects, while trials involving ferrets reached 100%, the experts said, noting that animals that received the vaccine also developed less severe symptoms and had lower viral loads.
So far, Ervebo has been approved as a vaccine for the Zaire strain of Ebola, the best-known variant and the one responsible for most outbreaks in recent decades. Currently, in the DRC, where 1,850 deaths have been recorded, the rarer Bundibugyo strain predominates, for which there is no authorized vaccine or specific treatment.
The first participant has been dosed in a CEPI-backed Phase 1 trial of @moderna_tx’s investigational vaccine against Bundibugyo virus, marking rapid progress in the global effort to combat the deadly Ebola outbreak in DRC.
Read more: https://t.co/rLSVKsT1Q7 pic.twitter.com/eMO1EfvNFX
— CEPI (@CEPIvaccines) August 4, 2026
The studies indicated that antibodies against the Bundibugyo strain generated by the Ervebo vaccine are weaker than those produced against Zaire Ebola, “but appear to have some neutralizing effect,” according to the panel of experts.
The advisory group was created after the WHO declared the DRC outbreak an international emergency on May 16. During its previous meetings, it had not recommended trials with Ervebo because it believed the vaccine first needed to be tested in specific research settings before its effectiveness could be evaluated.
After evaluating the potential vaccine’s safety, effectiveness and availability, the experts agreed there are no risks in conducting randomized trials in which contacts of infected people in the current outbreak are vaccinated.
On July 31, the current epidemic became the second-largest Ebola outbreak in history by number of infections and the largest in terms of infections ever recorded in the DRC, surpassing the outbreak that also occurred in eastern Congo between 2018 and 2020, which caused 2,299 deaths and 3,481 cases.
It is the 17th Ebola epidemic to affect the DRC and the one with the fastest growth in infections compared with any previous outbreak since its declaration.
However, it is still far from the worst Ebola epidemic in history, which took place in West Africa between 2014 and 2016 and caused about 11,000 deaths and 28,000 infections.
teleSUR/ JF
Sources: WHO – EFE
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