Scientists have revealed that 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 1 clinical trial.
The candidate vaccine, which was 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 interim results are reported online in advance of print in the New England Journal of Medicine.
NIAID Director Anthony S. Fauci, M.D., said that 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 and undoubtedly will be critically important in preventing future large outbreaks.
Fauci said that 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 vaccine contains segments of Ebola virus genetic material from two virus species, Sudan and Zaire. The Ebola virus genetic material is delivered by a carrier virus (chimpanzee-derived adenovirus 3 or cAd 3) that causes a common cold in chimpanzees but causes no illness in humans. The candidate vaccine does not contain Ebola virus and cannot cause Ebola virus disease.
The trial enrolled volunteers between the ages of 18 and 50. Ten volunteers received an intramuscular injection of vaccine at a lower dose and 10 received the same vaccine at a higher dose. At two weeks and four weeks following vaccination, the researchers tested the volunteers' blood to determine if anti-Ebola antibodies were generated. All 20 volunteers developed such antibodies within four weeks of receiving the vaccine.
Antibody levels were higher in those who received the higher dose vaccine.
The experimental NIAID/GSK vaccine did induce a T-cell response in many of the volunteers, including production of CD8 T cells, which may be an important part of immune protection against Ebola viruses. Four weeks after vaccination, CD8 T cells were detected in two volunteers who had received the lower dose vaccine and in seven of those who had received the higher dose.