For more than a year and a half, three of the world’s poorest countries have struggled against the most devastating Ebola epidemic in human history.Containing this unprecedented outbreak would have been a huge challenge for Guinea, Liberia and Sierra Leone under any conditions. But the scale of the task was far greater because of the absence of the most effective possible defence: a vaccine.
That may all be about to change. I normally like to avoid superlatives when describing the interim results of a medical trial, but it is difficult to talk about the report of the experimental Ebola vaccine in the Lancet as being anything less than spectacular. More than 7,600 people in Guinea have received the vaccine, known as rVSV-ZEBOV, in a study that targeted people from communities with cases of Ebola. None who received it immediately has so far contracted the virus. That’s an efficacy of 100%. And not only has it been shown to be so effective, it has also been well tolerated, with few side effects. This is rare for vaccines such as this one that contain a live virus, and it’s something to be thankful for.
Ebola vaccine trial proves 100% successful in Guinea
It is in fact incredibly unusual for any vaccine to show such efficacy, and so swiftly, too. For comparison, not long ago the results of trials for new malaria and dengue fever vaccines showed just how challenging development is. While they were promising, their effectiveness was much more limited
A traditional trial with a placebo control would have been contentious and politically unacceptable, given the known mortality of Ebola and the lack of other options for prevention or treatment. To substitute a potentially life-saving vaccine for an inert substance, given the circumstances, would not have been ethical – but a comparison still needed to be made. So half of the volunteer participants were vaccinated immediately, and the other half after a three-week delay. None of those vaccinated immediately were infected, compared with 16 out of more than 2,000 in the delayed group. Importantly, there is evidence that not only are those who receive the vaccine protected, but that by interrupting transmission, others in the community are protected too. This could prove crucial to ending the epidemic.
The GAVI Alliance is the global organisation that has earmarked $390 million to extend availability of the VSV-ZEBOV vaccine beyond Guinea, the country where it has been successfully tested on more than 7500 people.
The epidemic is now largely under control, but there have been 28,000 cases leading to 11,000 deaths in Guinea, Sierra Leone and Liberia. But cases are still coming to light, and the virus is still at large, lurking in the body fluids of survivors for as long as 6 months.
Although the trial isn’t yet over, the WHO could theoretically issue an Emergency Use Authorisation before it ends. This would enable the vaccine to be legally deployed where need
SOURCE – Guardian UK, New Scientist