WHO says experimental vaccine was tested on nearly 6,000 patients in Guinea who became virus-free within 10 days.
Scientists have struggled to develop an Ebola vaccine over the years, and this is the first one proven to work Spread through direct contact with the bodily fluids of victims or corpses, Ebola has killed more than 11,300 people, mostly in West Africa, since December 2013.
« It’s the first vaccine for which efficacy has been shown, » said Dr Marie-Paule Kieny, a WHO assistant director-general and the study’s lead author.
She added that other Ebola vaccines were underdoing testing, and that a vaccine was also needed to protect against a second strain, Sudan.
According to the Lancet medical journal, which published the findings on Thursday, the vaccine was given to about 5,800 people in Guinea last year.
After 10 days, all of those who received treatment were virus free.
The vaccine proved so effective that the study was stopped midway so that everyone exposed to Ebola in Guinea could be immunised.
The vaccine had few side effects, and although three people had strong reactions to it, none were affected long term.
Pharmaceutal company Merck is expected to seek regulatory approval in the US and Europe sometime next year.
Ebola first turned up in Africa in 1976 and had caused periodic outbreaks mostly in central Africa, but never with results as deadly as the West Africa outbreak.