Could vaccines against Zaire Ebola virus also protect against Bundibugyo virus?

The Institute of Tropical Medicine (ITM) and the Congolese Institut National de Recherche Biomédicale (INRB) are launching a study into the potential protection offered by existing Ebola vaccines against the Bundibugyo Ebola virus. The researchers are analysing blood samples from more than 600 people who have previously been vaccinated against the Zaire Ebola virus. The initial results are expected within two to six months. The project is supported by CEPI, the Coalition for Epidemic Preparedness Innovations.

There is currently no approved vaccine against the Bundibugyo Ebola virus. There are candidate vaccines under development, but these are not yet available for use. Approved vaccines, however, do exist against the Zaire Ebola virus. Through the EBO-BOOST-BRIDGE study, ITM and INRB aim to investigate whether these existing vaccines also elicit an immune response against the Bundibugyo virus.

Existing blood samples give researchers a head start

The study is using blood samples from more than 600 participants who received an approved vaccine against the Zaire Ebola virus during previous vaccination campaigns in the Democratic Republic of the Congo. This allows researchers to start quickly without first having to vaccinate new participants and monitor them over a long period. The laboratory tests are being carried out at ITM and INRB.

Better tests and faster vaccine development

The study aims to provide greater clarity on the immune response to the Bundibugyo virus, through both antibody and cellular immune responses. The results will help researchers develop laboratory tests for these antibodies. These tests are also important for future clinical trials. They can help determine which immune responses a vaccine elicits and whether certain antibodies are associated with protection against the disease.

In the longer term, the results may contribute to the development and evaluation of vaccines that could potentially provide protection against multiple Ebola strains.

Building on EBO-BOOST

EBO-BOOST-BRIDGE builds on the CEPI-funded EBO-BOOST Phase II study. In that study, ITM and INRB investigated the immune response following revaccination against the Zaire Ebola virus. The associated biobank contains blood samples from more than 600 participants. By re-analysing these existing samples, researchers can determine to what extent the antibodies generated also react to the Bundibugyo Ebola virus.

Strengthening laboratory capacity in the DRC

The project is one of four CEPI-supported studies investigating the potential immune responses elicited by existing Ebola vaccines to the Bundibugyo virus. CEPI has awarded US$1.02 million to the project. Part of the funding will be used to strengthen the INRB’s laboratory capacity, enabling it to operate in accordance with the same international standards and to respond more quickly to future Ebola outbreaks.

Part of a broader European collaboration

This work forms part of a broader European collaboration on Ebola vaccines. In May 2026, a working group of vaccine immunology laboratories was established within the European Vaccine Hub (EVH) to standardise tests for immune responses. By using the same methods, researchers can better compare results and assess new Ebola vaccines quicker and more reliably.

The study is funded by the Coalition for Epidemic Preparedness Innovations (CEPI) and the Belgian Directorate-General for Development Cooperation and Humanitarian Aid (DGD).