WASHINGTON - An experimental vaccine to prevent Ebola virus disease was well-tolerated and produced immune system responses in all 20 healthy adults who received it in a phase one clinical trial, the US National Institutes of Health (NIH) said Wednesday.

The candidate vaccine, co-developed by the NIH's National Institute of Allergy and Infectious Diseases (NIAID) and GlaxoSmithKline (GSK), was tested at the NIH Clinical Center in Bethesda, Maryland.

The results were reported online in the New England Journal of Medicine.

"The unprecedented 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," NIAID Director Anthony Fauci said in a statement.

"Based on these positive results from the first human trial of this candidate vaccine, we are continuing our accelerated plan for larger trials to determine if the vaccine is efficacious in preventing Ebola infection."

The candidate vaccine contains segments of Ebola virus genetic material from two strains of the Ebola virus -- the Sudan strain and the Zaire strain, which is responsible for the current Ebola outbreak in West Africa, but it cannot cause Ebola virus.

The Ebola virus genetic material is delivered by a carrier virus that causes a common cold in chimpanzees but causes no illness in humans.