WHO Calls for Clinical Trial of Ervebo Vaccine in Congo
Outbreak in the Democratic Republic of Congo surpasses 4,000 cases, and a specific vaccine for the Bundibugyo variant does not yet exist.
Outbreak in the Democratic Republic of Congo surpasses 4,000 cases, and a specific vaccine for the Bundibugyo variant does not yet exist.
The World Health Organization (WHO) on Friday called for a clinical trial of the existing Ervebo vaccine to curb the Ebola outbreak in the Democratic Republic of Congo (DRC). There, the 17th outbreak of the disease in the country's history has been raging for months, caused by the Bundibugyo variant, for which there is still no approved specific vaccine.
According to data released by DRC authorities, the total number of confirmed cases has reached 4,053, with 1,850 deaths from the infection. This outbreak, declared on May 15, 2026, after a delay of several weeks, is already considered the largest in the history of the African nation. WHO chief Tedros Adhanom Ghebreyesus said on platform X that preliminary data on Ervebo's effectiveness are "good news."
Ervebo, the only licensed Ebola vaccine, was developed by the American pharmaceutical laboratory Merck to combat the Zaire strain. Although it is not intended for the new Bundibugyo variant, preliminary data suggest it provides some protection against it, at least in animals. WHO experts note that no major safety concerns have been observed, paving the way for evaluating the vaccine directly in a Phase 3 clinical trial, which is typically conducted on thousands of people.
The vaccine alliance Gavi, which created and funds the global Ebola vaccine stockpile, has announced it will provide doses of Ervebo to support the trials. The stockpile currently holds around 500,000 doses, with a portion permanently kept in the DRC due to frequent outbreaks. The details of the trial itself have not yet been finalized, but it should be conducted in Congo, the only country where the Bundibugyo variant is currently circulating.
Despite Ervebo's potential, the priority remains finding a vaccine tailored to the new strain. Canada has already approved American pharmaceutical giant Moderna to launch clinical trials for its Bundibugyo vaccine. Two other candidates are in development: the "rVSV Bundibugyo" vaccine being developed by Hilleman Laboratories, which the WHO describes as "the most promising," and a vaccine from the University of Oxford, whose first volunteer received a dose in late July 2026. Trials for several potential treatments are also underway in parallel.
Ebola, which is transmitted through contact with bodily fluids and causes hemorrhagic fever, has claimed more than 15,000 lives in Africa over the past 50 years. AFP photographer Benedict Murhabazi captured dramatic scenes on June 23, 2026, in the city of Bunia, in eastern DRC, where health workers were transporting a patient infected with the virus.
