Doctors and researchers have been testing a vaccine to protect against Ebola in the west African nation of Guinea. Trials involving 4,000 people have now shown a 100% success rate in preventing infection. "When Ebola flared up in a village, researchers vaccinated all the contacts of the sick person who were willing — the family, friends and neighbors — and their immediate contacts. Children, adolescents and pregnant women were excluded because of an absence of safety data for them. In practice about 50% of people in these clusters were vaccinated. To test how well the vaccine protected people, the cluster outbreaks were randomly assigned either to receive the vaccine immediately or three weeks after Ebola was confirmed. Among the 2,014 people vaccinated immediately, there were no cases of Ebola from 10 days after vaccination — allowing time for immunity to develop — according to the results published online in the Lancet medical journal (PDF). In the clusters with delayed vaccination, there were 16 cases out of 2,380."
