Ebola vaccine is 100% successful

An Ebola vaccine has shown 100% success in an initial trial, the World Health Organisation reports.

The Ebola vaccine rVSV Zebov-GP being prepared for injection, Guinea. Credit: WHO

Results from an interim analysis of the Guinea Phase III efficacy vaccine trial show that VSV-EBOV (Merck, Sharp & Dohme) is highly effective against Ebola. The independent body of international experts – the Data and Safety Monitoring Board – that conducted the review, advised that the trial should continue. Preliminary results from analyses of these interim data are published in British journal The Lancet.

"This is an extremely promising development," said Dr Margaret Chan, Director-General of the World Health Organisation (WHO). "The credit goes to the Guinean Government, the people living in the communities and our partners in this project. An effective vaccine will be another very important tool for both current and future Ebola outbreaks."

While the vaccine up to now shows 100% efficacy in individuals, more conclusive evidence is needed on its capacity to protect populations through what is called “herd immunity”. To that end, the Guinean national regulatory authority and ethics review committee have approved continuation of the trial.

Team 9 of the WHO Ebola vaccine trial, at work in Katongourou, Guinea. Credit: WHO

"This is Guinea’s gift to West Africa and the world,” said Dr Sakoba Keita, Guinea's national coordinator for the Ebola response. "The thousands of volunteers from Conakry and other areas of Lower Guinea, but also the many Guinean doctors, data managers and community mobilisers have contributed to finding a line of defence against a terrible disease."

"The 'ring' vaccination method adopted for the vaccine trial is based on the smallpox eradication strategy," said John-Arne Røttingen, Director of the Division of Infectious Disease Control at the Norwegian Institute of Public Health and Chair of the Study Steering Group. "The premise is that by vaccinating all people who have come into contact with an infected person you create a protective 'ring' and stop the virus from spreading further. This strategy has helped us to follow the dispersed epidemic in Guinea, and will provide a way to continue this as a public health intervention in trial mode."

The vaccination trial began in late March and ended in late July 2015. The study compared two groups – given a single dose either immediately or delayed for 21 days. In the 90 clusters who received either immediate vaccination (48; 4123 adults vaccinated) or delayed vaccination (42; 3528 adults vaccinated on day 21), a single intramuscular injection of VSV-ZEBOV gave complete (100%) protection against Ebola 10 days after randomisation.

"Before the trial started, in most clusters there had been a series of Ebola cases over the weeks prior to randomisation.  However, since the trial started, we have seen no new cases in vaccinated volunteers within 10 days of vaccination, regardless of whether vaccination was immediate or delayed," explains co-author Dr Marie Paule Kieny, from the World Health Organisation (WHO) in Geneva, Switzerland.

The Ebola vaccine needs to be kept at a temperature of -80°C (-112°F). These vaccine storage devices use jet fuel
to keep the right temperature for up to 5 days in the field, even if the storage container is opened several times a day.
Here a vaccine core is being inserted into the storage device. Credit: WHO

"This is a remarkable result which shows the power of equitable international partnerships and flexibility," said Jeremy Farrar, Director of the UK's Wellcome Trust, one of the funders of the trial. "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. We, and all our partners, remain fully committed to giving the world a safe and effective vaccine."

"Ebola has claimed thousands of lives and devastated communities across West Africa," said UK international development secretary, Justine Greening. "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."

"This record-breaking work marks a turning point in the history of health R&D," said Assistant Director-General Marie-Paule Kieny, who leads the Ebola Research and Development effort at WHO. "We now know that the urgency of saving lives can accelerate R&D. We will harness this positive experience to develop a global R&D preparedness framework so that if another major disease outbreak ever happens again, for any disease, the world can act quickly and efficiently to develop and use medical tools and prevent a large-scale tragedy."

The trial design was developed by a group of experts from Canada, France, Guinea, Norway, Switzerland, the UK, USA, and WHO. The group included Professor Donald A. Henderson of John Hopkins University, who led the WHO smallpox eradication effort by using the ring vaccination strategy.

Cumulative totals of Ebola cases and deaths over time, April 2014 to July 2015. By Leopoldo Martin R [CC BY-SA 3.0], via Wikimedia Commons

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