Global health authorities are racing to identify medical options to help contain an Ebola outbreak in the eastern Democratic Republic of Congo, linked to the Bundibugyo strain of the virus. Unlike for the more common Zaire strain, there are no approved vaccines or treatments for the Bundibugyo ebolavirus (BDBV). Government data indicates that the latest outbreak has led to 2,473 confirmed cases, including 999 deaths. BDBV has a fatality rate of up to 40%.
Because there are no currently approved medical countermeasures for this specific strain, a small number of experimental vaccines and therapies are being assessed. Global health authorities are examining whether any existing Ebola treatments might offer protection, though such applications are currently supported only by limited animal data. Most experimental treatments have not yet been tested in humans and would require emergency or compassionate-use authorization before they are deployed in Congo. The World Health Organization (WHO) has recommended prioritizing several experimental drugs, including antibodies, antivirals, and vaccines, for the treatment and prevention of BDBV.
Vaccine Candidates Under Investigation
The University of Oxford launched the first human trial of a vaccine against Bundibugyo ebolavirus in July to evaluate safety and immune response in 50 healthy adults aged 18 to 55 in Oxford. The vaccine is based on ChAdOx1 technology, which was used in the Oxford/AstraZeneca COVID-19 vaccine, and is being manufactured by the Serum Institute of India (SII). SII has manufactured and stockpiled approximately 620,000 doses of the experimental vaccine candidate in anticipation of later-stage trials and potential emergency use if it proves effective, and it has supplied 4,000 doses for the early-stage trial. The Coalition for Epidemic Preparedness Innovations (CEPI) stated it would initially invest up to $8.6 million for the development of the shot. The WHO noted that experts considered a single dose of this vaccine candidate potentially suitable for contacts of Ebola cases, while a two-dose regimen might be used for high-risk but unexposed groups, including healthcare workers and frontline responders.
Additionally, the WHO said in May that a single-dose rVSV Bundibugyo vaccine being developed by the International AIDS Vaccine Initiative is the most promising candidate to prevent BDBV. The vaccine, rVSVΔG/BDBV-GP, uses the same technology as Merck’s approved shot Ervebo for the Zaire strain and has shown survival benefit in non-human primates in a 2023 proof-of-concept study. The WHO stated that the vaccine’s development would likely take seven to nine months before it is ready for assessment in a clinical trial. The International AIDS Vaccine Initiative is advancing the candidate toward a clinical trial and preparing for manufacturing, including transferring the vaccine virus and processes for good manufacturing practices production. CEPI has committed to an initial funding of $3.2 million to advance the vaccine candidate.
Other efforts include Moderna, which has partnered with CEPI to advance its mRNA-based BDBV vaccine candidate into pre-clinical and early clinical testing. CEPI has committed up to $50 million to support development, including manufacturing and progression to later-stage trials if early safety and immunogenicity data are positive. Furthermore, the privately held firm Public Health Vaccines is developing an experimental rVSV Bundibugyo virus vaccine, similar to Merck’s Ervebo. CEPI said it would provide $1.9 million in funding to advance this candidate into early clinical testing.
Antibody-Based Therapies
The WHO has recommended prioritizing privately held Mapp Biopharmaceutical’s pan-ebolavirus antibody drug, MBP134—a combination of two human monoclonal antibodies—for clinical trials among confirmed cases.
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