An experimental Ebola vaccine from GlaxoSmithKline is being fast-tracked into human studies and the company plans to build a stockpile of up to 10,000 doses for emergency deployment, if results are good.
The research work is being accelerated with funding from an international consortium, reflecting mounting concern over the worst outbreak of the disease that has killed more than 1,500 people in West Africa.
GSK's candidate vaccine, being co-developed with the U.S. National Institutes of Health, is expected to be given to healthy volunteers in Britain and the United States from about mid-September, with the program then being extended to Gambia and Mali.
Britain's biggest drugmaker said on Thursday the Phase I trials would start as soon as they received ethical and regulatory approvals.
The NIH's National Institute of Allergy and Infectious Diseases is also working on a wider program of clinical trials, including tests of a version of the GSK vaccine that may fight a second strain of Ebola, as well as the West African one.
In addition, U.S. researchers plan human tests of a vaccine developed by Canadian government scientists, which has been licensed to NewLink Genetics.
The trials being announced will enroll healthy volunteers with the goal of determining whether the vaccine is safe and whether it provokes a protective immune response.
The aim is to complete these tests by the end of 2014, after which vaccines could be deployed on an emergency basis.
In a grim assessment of the deadly disease, the World Health Organization said on Thursday that the current Ebola outbreak was continuing to accelerate and could infect more than 20,000 people.
Jeremy Farrar, director of the Wellcome Trust medical charity, which is helping to fund the vaccine trials, said the effectiveness of vaccines and drugs could only be assessed during epidemics, so it was vital to test products now.
GSK plans to begin making up to about 10,000 additional doses of its vaccine at the same time as the initial clinical trials, so if they are successful vaccine could be made available immediately for an emergency immunization program.
NewLink has also contracted for the manufacture of increased supplies of its vaccine.
A steering committee made up of senior officials from NIH and the U.S. Department of Defense also approved last week the first step toward using three advanced laboratories to manufacture Ebola vaccines and treatments, a person familiar with the planning told Reuters.
The three labs, in Texas, Maryland and North Carolina, were set up in 2012 by the U.S. Department of Health and Human Services in partnership with private industry to respond to pandemics or chemical, biological, radiological or nuclear threats..
The GSK vaccine consists of a common cold virus, called an adenovirus, that has been engineered to carry two genes of the Ebola virus. Animal testing has shown that when the adenovirus infects cells the Ebola genes produce harmless proteins that stimulate the immune system to produce antibodies to Ebola.
GSK acquired the vaccine after buying Swiss-based biotech company Okairos for 250 million euros ($330 million) last year.