Ebola trial results 'promising'
An experimental Ebola vaccine has triggered promising immune responses from 20 healthy volunteers taking part in a preliminary trial.
The results suggest the vaccine should protect people against the deadly infection that has already claimed more than 5,000 lives since March.
Scientists are now preparing for larger trials in West Africa next year that will show definitively whether or not the vaccine works.
The vaccine co-developed by the drug company GlaxoSmithKline (GSK) and the US National Institutes of Health (NIH) contains pieces of genetic material from two strains of the virus.
It is delivered into the bloodstream by a chimpanzee version of the common cold virus that causes no illness to humans.
The Phase I safety trial in the US recruited 20 healthy volunteers between the ages of 18 and 50 who were given two different doses of the vaccine.
All of them developed Ebola-targeting antibodies in their blood within four weeks of being treated. Antibody levels were greater in those given the higher dose.
In many of the volunteers the vaccine also generated CD8 "killer" T-cells - a type of immune system cell that attacks and destroys dangerous infected cells. These may also prove to be an important part of the immune response against Ebola.
Dr Anthony Fauci, director of the NIH's National Institute of Allergy and Infectious Diseases (NIAID), said: "The unprecidented scale of the current Ebola outbreak in West Africa has intensified efforts to develop safe and effective vaccines, which may play a role in bringing this epidemic to an end and undoubtedly will be critically important in preventing future large outbreaks.
"Based on these positive results from the first human trial of this candidate vaccine, we are continuing our accelerated plans for larger trials to determine if the vaccine is efficacious in preventing Ebola infection."
The vaccine used in the trial is designed to protect against both the Sudan and Zaire strains of Ebola. The current outbreak was caused by the Zaire strain.
Early trials of a "monovalent" version of the vaccine that only targets the Zaire strain are under way in Oxford, Mali and Switzerland.
The desperate need for a vaccine has seen rival pharmaceutical companies scrambling to be first with an effective treatment.
Drug giants Merck & Co has paid at least 30 million US dollars (£19 million) for the rights to another experimental vaccine, rVSV-EBOV, developed by US company NewLink Genetics Corp.
Dr Jeremy Farra, director of the Wellcome Trust, Britain's biggest research charity, said: "This work is encouraging and another significant contribution to efforts to tackle the Ebola crisis.
"We need a variety of public health interventions if we are to impact on this and future outbreaks, and that must include vaccines. It is why we and our international partners are supporting accelerated development of several vaccine candidates, including this one, at the same time.
"We had more good news this week about another of these vaccines - rVSV-EBOV - with the announcement that Merck have struck a deal to scale up production and take it through clinical trials. It's important that this momentum is maintained and that these vaccines can move to being tested in countries affected by the epidemic as soon as possible."
The World Health Organisation (WHO) has reported that 600 new cases of Ebola were recorded in the worst affected countries in just the past week.
Since the start of the epidemic a total of 15,935 people have fallen ill with Ebola and of those 5,689 have died.
Infection rates appear to be stabilising in Guinea and stabilising or declining in Liberia, but increasing in Sierra Leone, said the WHO.