WASHINGTON - The US government announced Thursday it will start initial human testing of an investigational vaccine next week to prevent infection of the Ebola virus that has killed more than 1,500 people in West Africa.

The US National Institutes of Health (NIH) said in a statement that the phase one clinical trial will determine if a vaccine, co-developed by the agency's National Institute of Allergy and Infectious Diseases (NIAID) and GlaxoSmithKline (GSK), is safe and induces an adequate immune response.

Testing will take place at the NIH's clinical center in Bethesda, Maryland, with 20 healthy adults aged 18 to 50 years receiving an intramuscular injection of the vaccine, it said.

In parallel, the NIH and a British consortium, including the Wellcome Trust, will test the NIAID/GSK vaccine among healthy volunteers in the United Kingdom and in the West African countries of Gambia and Mali, the agency said.

The US government is also discussing a trial of the vaccine in Nigeria, Africa's most populous country.

The NIH also said it will launch phase one clinical trials of another experimental Ebola vaccine developed by Canada's Public Health Agency in the fall.

"There is an urgent need for a protective Ebola vaccine, and it is important to establish that a vaccine is safe and spurs the immune system to react in a way necessary to protect against infection," NIAID Director Anthony Fauci said in the NIH press release.

GSK said in a statement that the British consortium that also involved the British government has pledged some 4.6 million US dollars for the phase one trials, which are expected to be completed by the end of 2014.

With the consortium's funding, GSK also said it will begin manufacturing up to around 10,000 additional doses of the vaccine at the same time as the initial clinical trials, so that if the trials are successful stocks could then be made available immediately to the World Health Organization to vaccinate people in high-risk communities.

According to the NIH and GSK, the NIAID/GSK Ebola vaccine is based on a type of chimpanzee cold virus, called chimp adenovirus type 3. The cold virus is used as a carrier, or vector, to deliver segments of genetic material derived from two Ebola virus species: Sudan Ebola and Zaire Ebola, which is the one circulating in West Africa.

The vaccine delivers the Ebola genetic material to human cells but does not replicate further. Rather, it allows the vaccine recipient's cells to express a protein, and that protein prompts an immune response in the individual, the NIH and GSK said.

Both stressed that the Ebola genetic material contained in the investigational vaccine cannot cause a vaccinated individual to become infected with Ebola.

"The experimental NIAID/GSK vaccine performed extremely well in protecting nonhuman primates from Ebola infection," Fauci said.

In response to the ongoing Ebola virus outbreak in West Africa, the pace of human safety testing for experimental Ebola vaccines has been expedited recently.

According to the World Health Organization, at least 1,552 suspected and confirmed deaths from Ebola infection have been reported in Guinea, Liberia, Nigeria, and Sierra Leone since the outbreak of the deadly virus was first reported in March 2014.

Clinical development for a vaccine is a three-phase process. During phase one, researchers test an investigational vaccine in a small group of people to evaluate its safety and the immune response it provokes. Phase two clinical trials of investigational vaccines are designed to further assess safety and immune response in larger numbers of volunteers. Phase three clinical trials are directed predominantly at determining vaccine's ability to prevent infection or disease known as efficacy.