WHO Urges Ervebo Vaccine Trial in DR Congo Ebola Outbreak

World Health Organization vaccine experts have recommended a full-scale human trial of the Ervebo vaccine, the only approved Ebola vaccine, to assess its effectiveness against a deadly strain currently spreading in the Democratic Republic of Congo (DRC). While Ervebo has a proven track record against the more common Zaire strain of Ebola, early data, including animal trials, suggests it might also provide some protection against the less common Bundibugyo strain. This strain is responsible for the current outbreak in the DRC.

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The members recommended Ervebo, the only licensed Ebola vaccine, be prioritized for inclusion in a randomized clinical trial in the context of the ongoing outbreak.

The recommendation was made as the number of confirmed Ebola cases in the DRC has exceeded 4,000, with over 1,850 fatalities reported. WHO Director-General Tedros Adhanom Ghebreyesus expressed concern, warning that the virus is spreading at a pace that outstrips containment efforts. The WHO's technical advisory group on candidate vaccine prioritization met recently to review emerging data on the Bundibugyo outbreak.

Experts unanimously agreed that using Ervebo in a clinical research study, specifically a "ring trial" involving close contacts of confirmed cases, poses no safety concerns. The vaccine has already been administered to hundreds of thousands of people across Africa and is licensed by regulatory agencies. However, the experts cautioned that expectations should be managed, as the vaccine's efficacy against symptomatic disease and transmission might not be high, although it could offer protection against fatal outcomes.

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Expectations need to be managed about its likely protective effect if used in a Phase III ring vaccination trial as efficacy against symptomatic disease and transmission may not be high, whereas protection against a fatal outcome may be achieved.

While a specific vaccine for the Bundibugyo strain remains the preferred long-term solution, and two potential vaccines are in early human trials, the current recommendation focuses on leveraging the existing Ervebo vaccine. The outbreak is primarily concentrated in the northeastern Ituri province, accounting for about 87 percent of cases, with a smaller percentage in the neighboring North Kivu province. Ebola is transmitted through contact with bodily fluids and causes hemorrhagic fever.

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The virus was spreading faster than response efforts can catch up.