An experimental Ebola vaccine from GlaxoSmithKline is being fast-tracked into clinical trials with human patients, and the company plans to immediately begin building a stockpile of up to 10,000 doses for emergency deployment if results are good.

The research 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 is being co-developed with the US National Institutes of Health (NIH). It is expected to be given to healthy volunteers in the UK and US from about mid-September as soon as ethical and regulatory approvals are received. The program will then be extended to Gambia and Mali.

The vaccine consists of an adenovirus that has been engineered to carry two genes of the Ebola virus. Animal testing is said to have shown that when the adenovirus infects cells the Ebola genes produce harmless proteins that stimulate the immune system to produce antibodies to Ebola.

Britain's largest pharmaceutical producer acquired the vaccine with the 2013 takeover of Swiss-based biotech company Okairos for €250 million.

According to the news agency Reuters, 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, US researchers plan human tests of a vaccine developed by Canadian government scientists and licensed to NewLink Genetics, which also has contracted for the manufacture of increased supplies of its vaccine.

These trials 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.

A steering committee of senior officials from NIH and the US Department of Defense also has approved 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 (HHS) in partnership with private industry to respond to pandemics or chemical, biological, radiological or nuclear threats.

In its latest assessment of the deadly disease, the World Health Organization said the current Ebola outbreak is continuing to accelerate and could infect more than 20,000 people.