WHO: Phase 3 Ervebo Trial Testing Vaccine's Cross-Protection Against Bundibugyo Virus Begins in Ituri

The World Health Organization announced 21 September 2026 that a Phase 3 clinical trial of the Ervebo (rVSV-ZEBOV) vaccine — testing its cross-protection against Bundibugyo ebolavirus, the strain driving the 2026 outbreak — has begun in Ituri province, the epicenter. The trial targets frontline health workers and other high-exposure outbreak-response personnel and draws on 20,000 of the 70,000 Ervebo doses the ICG mechanism released to DRC on 20 August (the remaining 50,000 are earmarked for the separate compassionate-use campaign for frontline and health workers, which had already expanded to Bunia and Mongbwalu, Ituri on 19 September alongside MSF/Epicentre's parallel BRAVO effectiveness study). WHO reiterated that Ervebo is 'highly effective' against the more common Zaire ebolavirus but its protection against Bundibugyo virus remains scientifically unproven, which is the trial's core question. As of the article's data, the outbreak stood at over 7,600 confirmed cases and more than 3,670 deaths, with nearly 80% of infections concentrated in Ituri; children account for roughly 25% of cases but 33% of deaths, with a case-fatality rate exceeding 60% in children under five versus well under half that among adults.