World Health Organization has expressed confidence that a prototype vaccine for Ebola may be 100 per cent effective in protecting against the deadly virus Ebola. It said the vaccine could become available in 2018 under a fast-track approval process. <br/><br/>The Lancet medical journal reported that in a major clinical trial, nearly 6,000 people in Guinea were given the test vaccine last year, and it was observed that not one of the 6,000 contracted the disease.<br/><br/>But in a control group of volunteers that did not receive the vaccine, 23 Ebola cases occurred. Marie-Paule Kieny, WHO's assistant director-general and lead author of the study, told AFP that these results strongly suggests that the vaccine could be up to 100 percent effective.<br/><br/>First identified in 1976 in the Democratic Republic of Congo, the Ebola virus erupted periodically mainly across west and east Africa in early 2014, mainly in Guinea, Liberia and Sierra Leone. <br/><br/>With a mortality rate above 40 per cent, the disease has an incubation period of up to three weeks. It causes violent and painful symptoms, including vomiting, diarrhoea, organ failure and internal bleeding.