World on the verge of an effective Ebola vaccine

3 August 2015

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 today in the British journal The Lancet. Acess the article here.

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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.

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. To date, over 4 000 close contacts of almost 100 Ebola patients, including family members, neighbours, and co-workers, have voluntarily participated in the trial.
The 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 3 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 include 13 to 17-year-old and possibly 6 to 12-year-old children on the basis of new evidence of the vaccine’s safety.

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.

Documents to download

VSV-EBOV was developed by the Public Health Agency of Canada. The vaccine was licensed to NewLink Genetics, and on 24 November 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 3 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.

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