cientists have finally developed a vaccine that can protect patients against the deadly Ebola virus.
The World Health Organisation (WHO) announced on Friday that one of the candidate vaccines developed in a research project by pharmaceutical company Merck Sharp & Dohme has been found to offer 100% protection against Ebola in humans.
This is great news, but the WHO said more conclusive evidence was needed to prove the vaccine’s capacity to protect populations through what is called “herd immunity”.
Herd immunity is a form of immunity that occurs when the vaccination of a significant portion of a population provides a measure of protection for others who have not developed immunity.
Preliminary results of the vaccine trial were published in The Lancet on Friday.
Dr Margaret Chan, WHO director-general, described the development of the trial, which was conducted in Guinea in west Africa, as “extremely promising. 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.”
Work on the trial began in affected communities in March. Researchers tested the effectiveness and safety of a single dose of the vaccine – called VSVEBOV – by using a ring vaccination strategy.
Ring vaccination is a process that involves health authorities reacting when a case is reported, then vaccinating those who have come into contact with the infected person.
More than 4 000 people who were in close contact with almost 100 Ebola patients, including family members, neighbours and co-workers, voluntarily participated in the trial. The confirmatory trials, which will test herd immunity, are expected to begin in Guinea soon.
The Guinean national regulatory authority and ethics review committee have already approved the continuation of the trial.
Dr Sakoba Keita, Guinea’s national coordinator for the Ebola response, said: “This is Guinea’s gift to west Africa and the world.”
Explaining the logic behind continuing with the ring vaccination, John-Arne Røttingen, director of the division of Infectious Disease Control at the Norwegian Institute of Public Health and chair of the study steering group, said: “The premise is that by vaccinating all people who have come into contact with an infected person, you create a protective ‘ring’ and stop the virus from spreading further.
“This strategy has helped us to follow the dispersed epidemic in Guinea, and will provide a way to continue this as a public health intervention in trial mode,” said Røttingen.
At the same time as the ring vaccination strategy is being conducted, international aid organisation Doctors Without Borders will conduct a trial of the same vaccine on frontline workers.
Bertrand Draguez, medical director at Doctors Without Borders, said: “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.”