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Ebola vaccine appeared safe, prompted immune responses
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Phase 1 clinical trial results suggest a bivalent Ebola vaccine was safe and immunogenic in healthy adults, according to the NIH.
The trial results were released ahead of print 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 and undoubtedly will be critically important in preventing future large outbreaks,” Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, said in a press release. “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.”
Anthony Fauci
The candidate vaccine, NIAID/GSK, which is being developed by the NIAID and a GlaxoSmithKline subsidiary, was tested in 20 healthy adults aged 18 to 50 years at the NIH Clinical Center in Bethesda, Md. Half the volunteers received an intramuscular injection in a dose of 2×1010 particle units, and half received a higher dose at 2×1011 particle units. The recombinant vaccine is derived from a chimpanzee adenovirus, delivering segments of genetic material from the Zaire ebolavirus and Sudan ebolavirus species. It causes no illness in humans, according to the NIH.
Within 4 weeks of vaccination, all volunteers developed antibodies against Ebola. Immune responses were dose dependent, with higher responses observed in those who were administered the higher dose vaccine. Previous research has shown that the vaccine elicits antibody responses and the production of T cells in nonhuman primates — sufficient to protect the animals against Ebola infection, researchers said.
The NIAID/GSK vaccine has prompted similar responses in humans, including the production of CD8 T cells detected in two volunteers who received the lower dose vaccine and in seven volunteers who received the higher dose, the NIH said.
“We know from previous studies in nonhuman primates that CD8 T cells played a crucial role in protecting animals that had been vaccinated with this NIAID/GSK vaccine and then exposed to otherwise lethal amounts of Ebola virus,” Julie E. Ledgerwood, DO, a researcher at the NIAID Vaccine Research Center and trial investigator, said in the release. “The size and quality of the CD8 T cell response we saw in this trial are similar to that observed in nonhuman primates vaccinated with the candidate vaccine.”
Julie Ledgerwood
According to the NIH, there were no serious adverse events associated with the vaccine. Two volunteers who received the higher dose, however, developed transient fever within 1 day of vaccination.
Two additional Ebola vaccines are currently in development, including a second NIH-sponsored vaccine candidate and another being developed by the Biomedical Advanced Research and Development Authority (BARDA) and Profectus BioSciences. Phase 2 trials of the NIAID/GSK vaccine are expected in 2015.
Additional information about the trial, VRC 207, can be found at http://www.clinicaltrials.gov using the identifier NCT02231866.
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