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Ebola vaccine trial proves 100% successful - 02 Aug 2015

A vaccine against Ebola has been shown to be 100% successful in trials conducted during the outbreak in Guinea and is likely to bring the west African epidemic to an end, experts say.

The results of the trials involving 4,000 people are remarkable because of the unprecedented speed with which the development of the vaccine and the testing were carried out.

Scientists, doctors, donors and drug companies collaborated to race the vaccine through a process that usually takes more than a decade in just 12 months.

This new vaccine, if the results hold up, may be the silver bullet against Ebola, helping to bring the current outbreak to zero and to control future outbreaks of this kind.

There have been a total of 27,748 cases of Ebola in Guinea, Liberia and Sierra Leone up to 26 July, with 11,279 reported deaths, although the outcome of many cases is unknown and the toll will be significantly higher. In the week ending 26 July, there were just four new cases in Guinea and three in Sierra Leone.

Because of the diminishing number of Ebola cases in west Africa and the shifting nature of the epidemic, with many sudden small outbreaks occurring across the region, researchers hit on a novel design for the trial. When Ebola flared up in a village, researchers vaccinated all the contacts of the sick person who were willing – the family, friends and neighbours – 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 (link to full publication). In the clusters with delayed vaccination, there were 16 cases out of 2,380.


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