Experts are reporting 100 per cent success rate in a trial for a new Ebola vaccine in Guinea.

The World Health Organisation (WHO) says initial results from trials of Merck and NewLink Genetics' VSV-ZEBOV vaccine on around 4,000 people showed complete protection after 10 days.

The people involved in the study had been in close contact with a confirmed Ebola case.

Health specialists around the world have described the results as “remarkable” and “game changing”.

“We believe that the world is on the verge of an efficacious Ebola vaccine,” WHO vaccine expert Marie Paule Kieny said at a briefing in Geneva.

The results could “change the management of the current Ebola outbreak and future outbreaks”, according to WHO director-general Margaret Chan.

“These communities need an effective vaccine sooner rather than later,” said Seth Berkley, CEO of The Gavi Alliance – a company that buys vaccines in bulk for poor countries who struggle to afford them.

Gavi says it will start buying the vaccine as soon as it is approved.

“We need to be ready to act wherever the virus is a threat.”

“It was a race against time and the trial had to be implemented under the most challenging circumstances,” said John-Arne Rottingen, a leader of the trial program from Norway's Institute of Public Health.

The trial in Guinea began in late March, evaluating the effectiveness and safety of a single dose of VSV-ZEBOV in a “ring vaccination” strategy.

The strategy involved dosing anyone with close contact to a person diagnosed with Ebola.

When the first people to be immunised began to show extraordinarily high protection rates, researchers decided to abandon their staggered strategy, because making people wait would be unethical and and unnecessary risk.

The trial “dared to use a highly innovative and pragmatic design, which allowed the team in Guinea to assess this vaccine in the middle of an epidemic”, according to Wellcome Trust director Jeremy Farrar, a leading infectious disease specialist.

“Our hope is that this vaccine will now help bring this epidemic to an end and be available for the inevitable future Ebola epidemics.”

Doctors without Borders (MSF) has called for VSV-ZEBOV to be rolled out to other centres of the outbreak; Liberia and Sierra Leone, where long chains of transmission along the virus outbreak to continue,

VSV-ZEBOV was originally developed within Canada's public health system, but was bought by NewLink Genetics and subsequently handed over to Merck for research, development, manufacturing and distribution duties.