Merck & Co's Phase III Ebola vaccine trial in Guinea has shown that its rVSV-ZEBOV drug candidate is 'highly effective' against Ebola.
The company's rVSV-ZEBOV drug candidate 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 the virus.
'This is an extremely promising development,' said Dr Margaret Chan, Director-General of the World Health Organisation.
Preliminary conclusions from this study, which began on 23 March, were published on-line in The Lancet.
While the vaccine up to now shows 100% effectiveness 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 trial used the 'ring' vaccination 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 from spreading further.
It appeared that all vaccinated individuals were protected against Ebola virus infection within six to 10 days of vaccination.
To date, more than 4,000 participants have received the vaccine in the “Ebola ça suffit” or “Ebola, that’s enough” trial, which was conducted by a team that included researchers from the World Health Organisation (WHO), the Norwegian Institute of Public Health, the Health Ministry of Guinea and Médecins sans Frontières, among others.
This record-breaking work marks a turning point in the history of health R&D
The trial stopped randomisation on 26 July to allow for all people at risk to receive the vaccine immediately, and to minimise 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 has now stopped. 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.
In parallel with the ring vaccination, a trial of the same vaccine is also being conducted on frontline workers.
'Merck has an enduring commitment to develop vaccines and medicines that address the world’s most devastating infectious diseases,' said Dr Roger Perlmutter, President of Merck Research Laboratories. 'Building on pioneering early work by the Public Health Agency of Canada and NewLink Genetics Corporation, the extraordinary efforts of the team in Guinea and other experts have yielded interim results that suggest a potential role for our rVSV-ZEBOV vaccine in the fight against Ebola disease.'
'This record-breaking work marks a turning point in the history of health R&D,' added WHO's Assistant Director-General Marie-Paule Kieny, who leads the Ebola Research and Development effort at the organisation.
'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.'
In addition to the Phase III trial in Guinea, other studies evaluating the rVSV-ZEBOV vaccine include the STRIVE (Sierra Leone Trial to Introduce a Vaccine against Ebola) Phase III study currently being conducted by the Sierra Leone College of Medicine and Allied Health Sciences (COMAHS), Sierra Leone Ministry of Health and Sanitation and the US Centers for Disease Control and Prevention (CDC); and the PREVAIL (Partnership for Research on Ebola Vaccines in Liberia) Phase II study being conducted by a Liberia-NIH partnership in Liberia.