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.
“Having seen the devastating effects of Ebola on communities and even whole countries with my own eyes, I am very encouraged by today’s news,” said Børge Brende, the foreign minister of Norway, which helped fund the trial.
“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. I would like to thank all partners who have contributed to achieve this sensational result, due to an extraordinary and rapid collaborative effort,” he said on Friday.
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.
The “gold standard” approach would be to take a population at risk of Ebola and vaccinate half of them while giving the other half a placebo. Instead, the researchers used a “ring” design, similar to that which helped prove the smallpox vaccine worked in the 1970s.
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 (pdf). In the clusters with delayed vaccination, there were 16 cases out of 2,380.
In another precedent-breaker, the trial was sponsored by the World Health Organisation because “nobody wanted to step into this role so we took the risk”, said assistant director-general, Dr Marie-Paule Kieny.
Funding came from the Wellcome Trust and other partners including the governments of Norway and Canada. Others involved included Médecins sans Frontières, whose volunteer doctors were on the frontline, and the London School of Hygiene and Tropical Medicine. About 90% of the trial staff were from Guinea, a country where no clinical research had been carried out before. The vaccine is made by Merck.
Kieny said: “We believe that the world is on the verge of an efficacious Ebola vaccine.”
The trial will continue, but without randomisation, which means that in Guinea, where there have been 3,786 cases and 2,520 confirmed deaths, every contact of a person who develops Ebola – and their contacts – will be offered it. Work in Gabon has now established that the vaccine is safe for children and adolescents, so they will be offered it too.
In terms of vaccines which are usually trialled in hundreds of thousands of people, Kierny said the numbers were small but highly promising. It is likely when larger numbers are collected that efficacy will be between 75% and 100%.
The future of two other potential Ebola vaccines, one from GlaxoSmithKline and the other from Johnson and Johnson, is now in question, because there are too few cases of Ebola for their trials to be completed.
The authors of the research said the ring design made it “logistically feasible” to conduct trials even in poor countries in the middle of a fading epidemic and it was a promising strategy for the future.
“This trial dared to use a highly innovative and pragmatic design, which allowed the team in Guinea to assess this vaccine in the middle of an epidemic,” said Jeremy Farrar, director of the Wellcome Trust and one of the world’s leading experts on infectious disease. “It is a remarkable result which shows the power of equitable international partnerships and flexibility.
“Our hope is that this vaccine will now help bring this epidemic to an end and be available for the inevitable future Ebola epidemics. This partnership also shows that such critical work is possible in the midst of a terrible epidemic. It should change how the world responds to such emerging infectious disease threats.”
John-Arne Røttingen, the head of infectious disease control at the Norwegian Institute of Public Health and chair of the trial’s steering group, said it had been a race against time in the most challenging circumstances.
“We are really pleased with the interim results,” he said. “It is really important to add the vaccine to the traditional hygiene measures we have used in the response so far. I believe this will be an important contribution to getting down to zero cases.”
Médecins sans Frontières said it was keen for the vaccine to be used in Sierra Leone and Liberia, where there were still cases.
Bertrand Draguez, MSF’s medical director, said: “In parallel with the ring vaccination we are also conducting a trial of the same vaccine on frontline workers. These people have worked tirelessly and put their lives at risk every day to take care of sick people. If the vaccine is effective, then we are already protecting them from the virus.
“With such high efficacy, all affected countries should immediately start and multiply ring vaccinations to break chains of transmission and vaccinate all frontline workers to protect them.”
Margaret Chan, the director general of of the WHO, said the vaccine trial’s success was a promising development. “The credit goes to the Guinean government, the people living in the communities and our partners in this project.”
The British government contributed £1m of the trial funding and has said it will increase that amount to help allow the testing to continue.
“Ebola has claimed thousands of lives and devastated communities across west Africa,” the international development secretary, Justine Greening, said. “The results of these UK-backed vaccine trials are hugely promising and represent a significant breakthrough in our battle against this deadly disease. The vaccine offers hope for a future where we never have to face an Ebola epidemic like this again.”
Trial data will now go to regulatory agencies in the hope of getting a licence for the vaccine which will allow it to be stockpiled for future Ebola epidemics. It is likely to be used only for people at risk in outbreaks and not given to whole populations.
The rVSV-ZEBOV vaccine is sometimes known as the Canadian vaccine as it was originally developed by the Public Health Agency of Canada before being sold to Merck to bring conclude the testing.