Vaccines designed for Zaire ebolavirus activated immune responses that also recognised the related Bundibugyo virus, according to research published in the New England Journal of Medicine. The findings suggest existing vaccine stockpiles could potentially offer some protection during current outbreaks where no specific vaccine exists.
Uganda and the Democratic Republic of Congo are currently facing Bundibugyo virus outbreaks, which cause severe haemorrhagic fever with high fatality rates. No licensed vaccine or treatment exists specifically for this strain, and developing new vaccines takes years.
Researchers analysed 179 blood samples from adults and children in West Africa who had participated in the earlier PREVAC clinical trial. Participants had received one of two licensed Ebola vaccine regimens: a single-dose or booster version of the rVSV vaccine, or the two-dose Ad26.MVA vaccine. Samples were examined at 28 days and three months after vaccination.
Using a multiplex Luminex assay, researchers tested whether antibodies generated against Zaire ebolavirus could recognise and bind to the glycoprotein of Bundibugyo virus. Both vaccine regimens generated cross-reactive antibodies detectable in blood samples. Although antibody responses were lower than those against the Zaire strain the vaccines were designed to target, Bundibugyo-recognising antibodies were clearly present.
With the rVSV vaccine, these antibodies were detectable at 28 days and remained present at three months. For the Ad26.MVA vaccine, the antibody response strengthened at the three-month mark compared with one month.
The researchers clarified that whilst they demonstrated antibodies can bind to Bundibugyo virus, it remains unknown whether this is sufficient to prevent illness. Previous studies suggest glycoprotein-binding antibody levels are associated with protection after vaccination. Further clinical trials are needed to establish whether stockpiled vaccines can offer protection against Bundibugyo virus infection.
Source: Medical Xpress / New England Journal of Medicine (2026)
