Health and Medicine

Ebola Vaccine 100 percent Effective In Trial

Just in time to grant 2016 a little redemption comes the news that a trial of a vaccine against the Ebola virus has proven even more successful than expected. Without significant mutation, we will probably never again see a large outbreak of the disease.

An estimated 11,000 people died from the West African Ebola epidemic that started in 2013, more than had been killed in all previous outbreaks combined. Moreover, the damage done to medical systems in the most affected countries may have led to more deaths than the direct effect of the disease itself.

One of the few good things to come out of this was that the crisis pushed medical researchers worldwide to get on with making a vaccine. Early results looked promising, but it is only now, with publication in The Lancet, that the effectiveness of the rVSV-ZEBOV vaccine has been confirmed as long-lasting.

rVSV-ZEBOV expresses a protein also found on the surface of the Zaire Ebolavirus, the most dangerous form of the virus, stimulating an immune reaction. By the time it became available the disease was already in decline across most of the previously affected region, thanks to interventions reducing transmission. Nevertheless, a team led by Dr Ana Maria Henao-Restrepo of the World Health Organisation vaccinated 5,837 people in parts of Guinea and Sierra Leone where infections were still occurring, prioritizing those most likely to have been exposed.

Four vaccinated people came down with Ebola, but in all cases the timing suggests they had been infected beforehand. No vaccine recipient got sick with Ebola between six and 84 days after vaccination, let alone died from the disease. Meanwhile, people in the same communities who had refused vaccination, or otherwise missed treatment, continued to get sick.

Although slightly more than half those vaccinated reported side effects, these were overwhelmingly mild, with headache, fatigue, and temporary muscle pain being by far the most common. Eighty individuals experienced more severe sickness in the period after vaccination, but only two or three of these appear to have been related to the treatment, and all recovered.

Earlier research had shown the vaccine was effective for a period of three weeks, but with the discovery that Ebola can resurface long after it was thought to have been eliminated, longer-lasting protection took on renewed importance. It is only with the publication of this paper that we can be confident the rVSV-ZEBOV vaccine will provide the protection needed in cases of future outbreaks.

Ebola is also killing chimpanzees and gorillas, with up to 90 percent dying in localized outbreaks. The vaccine’s success increases the chance of ensuring their protection.

NPR has reported that 300,000 doses of the vaccine have been stockpiled in case of another outbreak.

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