A vaccine against the deadly Ebola virus has led to 100%protection and could transform the way Ebola is tackled, preliminary resultssuggest.
There were no proven drugs or vaccines against the virus at the start of the largest outbreak of Ebola in history, which began in Guinea in December 2013.
The World Health Organization (WHO) said the findings, being published in the Lancet, could be a "game-changer".
Experts said the results were "remarkable".
This trial centred on the VSV-EBOV vaccine, which was started by the Public Health Agency of Canada and then developed by the pharmaceutical company Merck.
It combined a fragment of the Ebola virus with another safer virus in order to train the immune system to beat Ebola.
A unique clinical trial took place in Guinea. When a patient was discovered, their friends, neighbours and family were vaccinated to create a "protective ring" of immunity.