The World Health Organization (WHO) today announced positive results from an interim analysis of the Guinea Phase III efficacy vaccine trial, demonstrating that the VSV-EBOV vaccine is highly effective against Ebola.
The Guinea vaccination trial began in affected communities in 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, neighbors, and co-workers, have voluntarily participated in the trial.
Preliminary analysis of the interim data was published today in the British journal The Lancet.
Based on positive data, the trial stopped randomization on July 26 to allow 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, a practice which will now stop.
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.
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.
“In parallel with the ring vaccination, we are also conducting a trial of the same vaccine on frontline workers,” said Bertrand Draguez, Medical Director at Médecins sans Frontières. “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.”
Scientists at the Public Health Agency of Canada’s National Microbiology Laboratory originally developed the VSV-EBOV vaccine candidate. It has been licensed to NewLink Genetics Corp., in collaboration with Merck Sharp & Dohme Corp (Merck). The Ebola virus genetic material is delivered by a carrier virus (recombinant Vesicular Stomatitis Virus, or rVSV). The candidate vaccine does not contain Ebola virus and cannot cause Ebola virus disease.
The trial is funded by WHO, with support from the Wellcome Trust, the United Kingdom Department for International Development, 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.
Read more: Efficacy and effectiveness of an rVSV-vectored vaccine expressing Ebola surface glycoprotein: interim results from the Guinea ring vaccination cluster-randomised trial (.pdf)