Can a vaccine built for one Ebola virus stop another? The World Health Organization is about to find out

The World Health Organization (WHO) has recommended prioritising the Ervebo vaccine for testing in a clinical trial in the Democratic Republic of the Congo. The vaccine was originally developed to protect against Zaire ebolavirus, the species responsible for the devastating west African epidemic just over a decade ago.

The recommendation comes as researchers develop vaccines and treatments for the ongoing outbreak in the Democratic Republic of the Congo (DRC).

Ashanom Ghebreyesus - director general of the World Health Organisation (WHO) - has warned the outbreak is "already the second-biggest Ebola epidemic on record"