The vaccine shows up to 100% efficacy in individuals, but more conclusive evidence is needed on its capacity to protect populations through what is called 'herd immunity' and the ability to interrupt transmission. Preliminary results from analyses of these interim data are published today in the journal The Lancet.
The Guinea vaccination trial began in affected communities on 23 March 2015 to evaluate the efficacy, effectiveness and safety of a single dose of the vaccine VSV-EBOV by using a 'ring' vaccination strategy. By vaccinating all people who have come into contact with an infected person you can create a protective ‘ring’ and stop the virus from spreading further.
So far, more than 7,600 people who have had close contact with Ebola patients, including family members, neighbours, and co-workers, have voluntarily participated in the trial.
An independent body of international experts - the Data and Safety Monitoring Board – have advised that the trial should continue. The Guinean national regulatory authority and ethics review committee have also approved continuation of the trial.
The Wellcome Trust, with contributions from DFID, have given more than £5.2 million to support clinical trials of the VSV-EBOV vaccine. The trial is being implemented by the Guinean authorities, WHO, Médecins sans Frontières (MSF) and the Norwegian Institute of Public Health, with support from a broad partnership of international and national organizations.
Dr Jeremy Farrar, Director of the Wellcome Trust, said: "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. It is a remarkable result, and one that 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 emerging infectious disease threats. We, and all our partners, remain fully committed to giving the world a safe and effective vaccine."
The VSV-EBOV trial stopped randomisation on 26 July to allow for all people at risk to receive the vaccine immediately, and to minimize the time necessary to gather more conclusive evidence needed for eventual licensure of the product. Until now, 50% of the rings were vaccinated three weeks after the identification of an infected patient to provide a term of comparison with rings that were vaccinated immediately. This now stops. In addition, the trial will now children on the basis of new evidence of the vaccine’s safety.
WHO Assistant Director-General Marie-Paule Kieny, who leads the Ebola Research and Development effort, said: "This record-breaking work marks a turning point in the history of health R&D. 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."
Dr. Sakoba Keita, Guinea’s national coordinator for the Ebola response, said: "This is Guinea’s gift to West Africa and the world. 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."
Dr Dan O’Connor, Head of Humanities and Social Science at the Wellcome Trust said: "The success of the ‘ring’ strategy is a hugely important step forward for research ethics. It shows not only that we can conduct urgently needed, rapid response research during epidemics, but that we can do so in a way that is both ethically sound and responsive to the needs of affected communities."
Henao-Restrepo A. M. et al. 'Efficacy and effectiveness of an rVSV-vectored vaccine expressing Ebola surface glycoprotein: interim results from the Guinea ring vaccination cluster-randomised trial'. The Lancet. 2015.
About the vaccine
VSV-EBOV was developed by the Public Health Agency of Canada. The vaccine was licensed to NewLink Genetics, and on November 24, 2014, Merck & Co., Inc and NewLink Genetics Corp. entered into an exclusive worldwide licensing agreement wherein Merck assumed responsibility to research, develop, manufacture, and distribute the investigational vaccine. Financial support was provided by the Canadian and US Governments, among others.
A ring vaccination protocol was chosen for the trial, where some of the rings are vaccinated shortly after a case is detected, and other rings are vaccinated after a delay of three weeks. This is an alternative to using a placebo by providing a randomized control group for comparison but at the same time ensures that all contacts are vaccinated within the trial.
The trial design was developed by a group of experts from Canada, France, Guinea, Norway, Switzerland, United Kingdom, United States, 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.
The partners: The Guinea Ebola vaccine trial is the coordinated effort of many international agencies. WHO is the regulatory sponsor of the study, which is implemented by the Ministry of Health of Guinea, WHO, Médecins sans Frontières (MSF), EPICENTRE and the Norwegian Institute of Public Health. The trial is funded by WHO, with support from the Wellcome Trust, United Kingdom, the Norwegian Ministry of Foreign Affairs to the Norwegian Institute of Public Health through the Research Council of Norway, the Canadian Government through the Public Health Agency of Canada, Canadian Institutes of Health Research, International Development Research Centre and Department of Foreign Affairs, Trade and Development and MSF. The trial team includes experts from The University of Bern, the University of Florida, the London School of Hygiene and Tropical Medicine, Public Health England, the European Mobile Laboratories among others.
Ebola and the Wellcome Trust
• Since the beginning of the outbreak in Liberia, Guinea and Sierra Leone, the Wellcome Trust has committed more than £10 million through its emergency Ebola research funding initiative, including £5.2m to support clinical trials of the vaccine VSV-EBOV. As well as supporting new approaches to treating, preventing and containing the disease, during the current epidemic, it also funded research into the ethical challenges of testing experimental medicines during epidemics.
• Wellcome Trust Director Jeremy Farrar was among a number of global health experts who first called for Africans to be given access to experimental vaccines and treatments. In August a WHO expert panel unanimously concluded that in such exceptional circumstances it would be ethical to evaluate unregistered investigational treatments in people with Ebola virus disease. He has since argued repeatedly for reform of the WHO to enable the world to be better prepared for emerging infectious disease threats.
• In addition to the ring vaccination trial of VSV-EBOV in Guinea, projects supported include:
Trials of another experimental vaccine, ChAd3 (chimp adenovirus type 3), co-funded by a £2.8 million grant from the Wellcome Trust, the Medical Research Council and the UK Department for International Development. A £3.2 million platform for evaluating experimental Ebola therapies, led by Professor Peter Horby of Oxford University. Two treatments, brincidofovir and TKM-Ebola-Guinea have been evaluated to date. Several projects through the Research for Health in Humanitarian Crises programme (R2HC), joint with the UK Department for International Development. These include a 15-minute diagnostic test to detect Ebola in saliva, a modelling tool to help predict the spread of cases in West Africa, and a behaviour change project that seeks to improve safety procedures for those working on the front lineNotes to editor.