An experimental Ebola vaccine being trialled in Guinea has shown to be 100% successful in protecting people from contracting the disease, according to preliminary results announced today. This is the first evidence that a vaccine could shield people from getting the disease, and offers hope that it could be used to finally conquer the ongoing outbreak in West Africa, and any future one that might spring up.  

“This is an extremely promising development,” announced Dr. Margaret Chan, director general of the World Health Organization. “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 was based on the smallpox eradication strategy, using what’s known as a “ring” vaccination technique. After a patient is diagnosed with Ebola, a person’s friends and families are all vaccinated to try and break the main routes of transmission, and stop it spreading further. The trial of this approach in Guinea involved over 4,000 people, and while these initial results show 100% efficacy, the researchers predict that this might fall to between 75 and 100% when larger trials are conducted.

Due to the ethical implications of giving people a placebo vaccination, the researchers instead went for a trial design in which one group of subjects were vaccinated soon after their relative was diagnosed with Ebola, while the second group waited three weeks before vaccination. They found that no one contracted the disease in the first group within the 10-day infection window, but 16 were diagnosed with Ebola in the second group during that same period.

The results, published in The Lancet, have been so successful that from now on the delayed vaccination group will be abandoned and all people who have come into contact with an Ebola patient will receive the vaccination. The trial also only focused on adults, and so now it looks likely that adolescents and children will receive the vaccination too.

The vaccine itself was created using an attenuated livestock virus that has been engineered to produce a particular Ebola protein called rVSV-ZEBOV. The production of the vaccine has been hailed as remarkable due to the unprecedented speed at which it has been developed; rather than taking decades, it has only been 12 months.  

“This is a remarkable result which shows the power of equitable international partnerships and flexibility,” said Jeremy Farrar, director of the Wellcome Trust, which was one of the funders of the trial. “This partnership also shows that such critical work is possible in the midst of a terrible epidemic. It should change how the world responds to such emerging infectious disease threats. We, and all our partners, remain fully committed to giving the world a safe and effective vaccine.”

While the vaccine has been shown to work “very well” for three weeks, now the researchers want to find out for exactly how long it offers protection. 

Main image: European Commission DG ECHO/Flickr CC BY-NC-ND 2.0