New Studies To Test Whether Existing Ebola Vaccines Can Generate Immune Responses To Bundibugyo Ebolavirus
CEPI-backed studies will analyse blood samples from thousands of people who have already been vaccinated against Zaire ebolavirus, with first results expected within months
CEPI is providing US$4.17 million to four research projects designed to assess whether vaccines already or previously licensed against Zaire ebolavirus—including Ervebo—could offer protection against Bundibugyo ebolavirus, the virus behind the rapidly escalating outbreak in the Democratic Republic of the Congo, which was declared a Public Health Emergency of International Concern by the World Health Organization (WHO) in May 2026. Awardees include research groups led by UCLA (USA); Institute of Tropical Medicine (Antwerp); University of Oxford (UK); and MRC-University of Glasgow Centre for Virus Research (UK).
“There is no licensed vaccine against Bundibugyo virus. CEPI is funding multiple Bundibugyo vaccine candidates to address this gap, but even on the most compressed timelines those vaccines will not be available for the earliest phase of this outbreak”, explains Dr Richard Hatchett, CEO of CEPI. “However, vaccines do exist for the related Zaire ebolavirus, including Ervebo. Given the recent announcement that Ervebo will be deployed for emergency use against Bundibugyo virus, these CEPI-backed studies will be all the more important to inform on how we can make the best use of the existing vaccine.”
How the studies support vaccine development
The research teams will analyse stored blood samples from individuals vaccinated with licensed/previously licensed vaccines against Zaire ebolavirus either in previous vaccination campaigns and/or clinical trials. They aim to characterise vaccine-induced immune responses and assess cross-reactivity of antibody responses against Bundibugyo ebolavirus.
The critical data that these serology studies will provide will help establish and standardise tests for antibodies against Bundibugyo virus and use longitudinal samples to define the dynamics and durability of these responses. Data from these studies will also aid interpretation of immune responses in clinical trials, help assess whether Bundibugyo-specific antibodies are associated with protection, and inform future vaccination strategies and evaluation of Bundibugyo-specific and broadly protective filovirus vaccines.
In recent weeks, new data have emerged indicating that further prospective evaluation of Ervebo is warranted. Consequently, the WHO Technical Advisory Group on Candidate Vaccine Prioritization (TAG-CVP) has recommended that Ervebo be evaluated in a Phase 3 clinical trial, in addition to Bundibugyo-specific vaccine candidates when they are ready. The DRC authorities and Africa CDC have announced plans to deploy Ervebo to priority groups under protocol-governed expanded use. The CEPI-backed studies will rapidly generate additional evidence to help fill outstanding gaps in knowledge, and contribute to decision making about how Ervebo can be used in this and future responses.