The results of the trial in Guinea were released in The Lancet.
When analysing the results, the teams didn't count people who got sick within the 10 days, as they were believed to have been infected before they received the vaccine.
"I really believe that now we have a tool which would allow (us) to control a new outbreak of Ebola of the Zaire strain", said Dr. Marie-Paule Kieny, a World Health Organization assistant director-general who was the study's lead author.
The vaccine was developed in Canada but is now owned and manufactured by Merck, Sharp & Dohme.
Ebola virus was first discovered in Africa in 1976, and there have been intermittent outbreaks on the continent ever since. But the 2013-2016 West African Ebola outbreak, which resulted in more than 11 300 deaths, highlighted the need for a vaccine. At a time when good news seems in short supply, a triumph over Ebola is great news indeed.
It involved tracing all people who may have come into contact with a confirmed Ebola cases (including clothes of the infected person) within the three-week incubation period of the virus. That meant 117 clusters, with rings of contacts around them consisting of about 80 people on average.
Initially, rings were randomised to receive the vaccine either immediately or after a 3-week delay, and only adults over 18 years were offered the vaccine. The shot also protected several monkeys who received it a day after being infected with Ebola.
Scientists have struggled to develop an Ebola vaccine over the years, and this is the first one proven to work. However, the authors note that the trial was not created to measure this effect, so more research will be needed.
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Some of these vaccines require two doses three weeks apart, and may confer a longer immunity. Approximately half reported mild symptoms soon after vaccination, including headache, fatigue and muscle pain but recovered within days without long-term effects. Two patients had serious reactions, including one who had an allergic reaction.
Among people who were not immediately given the vaccine, there were 23 cases.
"Ebola left a devastating legacy in our country", says Dr. KeÏta Sakoba, Director of the national agency for health security in Guinea, West Africa.
In January, GAVI, the Vaccine Alliance provided US$5 million to Merck towards the future procurement of the vaccine once it is approved, prequalified and recommended by WHO.
If all goes well, the vaccine could become available in 2018 under a fast-track approval process, it said. Merck and WHO's partners are working to compile data to support license applications.
And the collaborative way in which global groups worked together to develop and test the vaccine lays the groundwork for fighting the next epidemic.
It's the same strategy that was used to eradicate smallpox. It will submit the vaccine for licensing by the close of 2017. The vaccine does not contain any live Ebola virus. This suggests that the new vaccine provides 100 percent protection against the illness.