Ebolavirus species and vaccine specificity

Ebola is not a single virus. It is a group of related orthoebolaviruses, of which four are known to cause disease in humans, and the Zaire species has caused most of the large recorded outbreaks. Bundibugyo ebolavirus was first identified in Uganda in 2007. The distinction matters because immunity is largely species-specific: the licensed Ebola vaccine, Ervebo, protects against Zaire ebolavirus and cannot be assumed to protect against Bundibugyo. That leaves a real gap, because an outbreak of the Bundibugyo species would begin with no vaccine available at all. This trial is the first attempt anywhere to close that gap in humans. The viral vector approach used here takes a harmless modified chimpanzee adenovirus and uses it to deliver the genetic instructions for an ebolavirus protein, prompting the immune system to recognise the real virus later — the same method that made rapid COVID-19 vaccine development possible.