The World Health Organization began human trials of the VSV-ZEBOV vaccine across Guinea in March 2015An Ebola test vaccine provided blanket protection in a field trial in Guinea, researchers said, possibly heralding “the beginning of the end” for the devastating West African outbreak that has killed thousands. The serum was 100 percent effective after a week in more than 7,600 people inoculated, according to results published in The Lancet medical journal 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.