An Ebola test vaccine provided blanket protection in a field trial in Guinea, researchers have said, possibly heralding "the beginning of the end" for the devastating west African outbreak.
The serum was 100 percent effective, after a week, in more than 7600 people innoculated, according to results published in The Lancet on Friday and hailed as "extremely promising" by World Health Organization (WHO) chief Margaret Chan.
The world was "on the verge of an effective Ebola vaccine", the UN's health agency said in a statement.
"The initial results of the study show that the vaccine can effectively contain the further spread of the Ebola virus," said the University of Bern, which contributed to the research.
Though encouraging, the results are "interim" and the vaccine will not become immediately available as a community-wide Ebola shield, experts cautioned.
About 28,000 people have been infected in Guinea, Sierra Leone and Liberia since late 2013, according to the WHO. Nearly half have died, but there is thought to be a large undercount of cases and deaths.
Having brought an already fragile health sector to its knees, and driving out much-needed investment, the outbreak has started winding down but is not over.
Seven cases were confirmed the week ending in July 26 - four in Guinea and three in Sierra Leone - the lowest weekly total for more than a year.
But even a single undetected case can spark a flareup - the virus spreads through direct contact with body fluids.