Interim findings from a Phase 1 trial of an experimental Ebola vaccine showed it caused no serious side effects, and produced an immune response in participants within four weeks. The tests began in September and were conducted on 20 healthy adults, who were injected with a higher or lower dose of the vaccine.

The results showed a significantly better immune response with a higher dose of vaccine - meaning those volunteers receiving a higher dose produced more antibodies than those on a lower dose.

In addition, two of the lower dose group and seven in the higher developed a crucial kind of immune cell called CD8 T cells, an important part of the body's response against disease.

The vaccine itself did not expose the volunteers to the virus - instead, it contained genetic material from two Ebola strains. It used a modified chimpanzee cold virus to deliver segments of the genetic material - without the ability to spread through the body like Ebola, but able to prompt the antibody response.

The results were published on Wednesday in the New England Journal of Medicine.

'Encouraging'

"The safety profile is encouraging, as is the finding that the higher dose of vaccine induced an immune response quite comparable to that which has completely protected [lab] animals from Ebola," said Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases (NIAID).

The NIAID is developing the intramuscular vaccine alongside Okairos, a biotechnology company owned by GlaxoSmithKline.

None of the volunteers experienced serious side effects within the study period. Two, however, had a brief and mild fever 24 hours after the injection.

Fauci cautioned that the vaccine is still a long way from use in the field. No announcement on larger-scale trials is expected before early next year.

The trial is still ongoing and will monitor the participants for 48 weeks.

The rapid spread of the worst-ever outbreak of Ebola, a hemorrhagic fever, has left health agencies and pharmaceutical companies scrambling to fast-track experimental drugs and vaccines. The virus has killed some 5,500 people this year, mostly in West Africa.

jr/jm (Reuters, AFP)