Ebola Vaccine Trial Begins in DR Congo Amid Ongoing Bundibugyo Outbreak

VoS NEWS DESK | WORLD HEALTH | 22 SEPTEMBER 2026

The vaccination programme is taking place as the DRC continues to deal with one of its most serious Ebola outbreaks. The current epidemic is caused by the Bundibugyo virus, a different Ebola species from the Zaire virus targeted by Ervebo. WHO says there is currently no licensed vaccine specifically for Bundibugyo virus disease.

Ervebo is already a licensed and WHO-prequalified vaccine for Ebola virus disease caused by the Zaire species. However, its effectiveness against Bundibugyo virus in humans remains uncertain. WHO's Strategic Advisory Group of Experts on Immunization concluded that the available evidence is not sufficient to establish clinically meaningful protection against the current strain. For this reason, WHO recommends that Ervebo be used against Bundibugyo virus only within research protocols.

The trial is intended to provide stronger scientific evidence about whether the vaccine can offer protection. Health workers and other frontline responders are being prioritised because they face increased exposure while working in areas affected by the outbreak. Reports from Bunia, the centre of the outbreak in Ituri province, said health workers were among the first participants to receive doses.

The scale of the outbreak has also increased the urgency of the research. WHO reported that, by late August, confirmed Bundibugyo cases had been detected across 60 health zones in six provinces of the DRC, with Ituri remaining the main epicentre. WHO's latest assessment described the risk within the DRC as very high because of continued transmission and geographical expansion.

At the same time, researchers are studying potential treatments for patients already infected with the virus. WHO says the PARTNERS clinical trial, which began enrolling patients in July, is operating in several clinical management facilities in Ituri and has enrolled more than 300 confirmed cases.

WHO has also stressed that vaccination research is only one part of the response. Authorities and international partners continue to focus on surveillance, laboratory testing, contact tracing, infection prevention, clinical care and community engagement. Cross-border cooperation remains important because population movement creates a risk of further transmission beyond affected areas.

VoS STRATEGIC INSIGHT

The DRC vaccine trial could help answer an important scientific question: whether an existing Ebola vaccine can provide meaningful protection against a different Ebola species for which no licensed vaccine currently exists. Until reliable clinical evidence becomes available, WHO continues to emphasise that the vaccine's effectiveness against Bundibugyo virus remains unknown and that established outbreak-control measures must continue alongside the research.

Source: World Health Organization (WHO), PBS NewsHour, CIDRAP