The vaccine protected 100% of study participants in Guinea against the virus. Guinea’s pharmaceutical regulator and an ethics review committee have approved continuation of the trial to investigate herd immunity.
Merck & Co.’s VSV-EBOV is being developed as part of a licensing agreement with the Public Health Agency of Canada and NewLink Genetics. It is based on VSV, the vesicular stomatitis virus, engineered to express glycoproteins of the Zaire strain of Ebola virus.
Marie-Paule Kieney, head of Ebola vaccine research at the WHO, described the trial as “record-breaking” and a “turning point in the history of health R&D.”
“This is an extremely promising development,” added Margaret Chan, Director-General of the 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.”
The trial used a ring method based on the smallpox eradication strategy, vaccinating all people who have come into contact with an infected person to create a protective ring and stop the virus spreading further.
The “Ebola ça suffit” – “Ebola, that’s enough” – trial began on March 23, 2015 and has administered VSV-EBOV to more than 4,000 people - and more than 7,000 including the control wing. Adult volunteers were randomised into a group receiving an immediate dose, and a control arm vaccinated 21 days later.
Randomisation ended on July 26 to allow all at-risk people to receive a dose of the vaccine, and to more quickly gather conclusive evidence needed for licensing. The trial will also now expand to include volunteers between 13 and 17 years old, and possibly from as young as six years old.
Médecins sans Frontières (Doctors without Borders) revealed it is also conducting a trial of the same vaccine on frontline workers.
“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,” said Bertrand Draguez.
The Wellcome Trust, a British co-funder of the trial, called the results “remarkable”, while Guinea’s national coordinator for Ebola response, Sakoba Keita, described the vaccine candidate as 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.”
Merck & Co.’s vaccine previously showed success in preclinical trials on macaques.