WASHINGTON (CN) - With two experimental Ebola vaccines in the wings, the U.S. government said it needs volunteers for a large clinical trial that opened in Liberia on Wednesday.
Prevail, short for the Partnership for Research on Ebola Vaccines in Liberia, is a Phase II/III study, that requires approximately 27,000 healthy men and women, age 18 years and older, the National Institutes of Health (NIH) said.
A unit of that agency, the National Institute of Allergy and Infectious Diseases (NIAID), sponsors the trial, led by a recently formed Liberia-U.S. clinical research partnership.
"One vaccine candidate, cAd3-EBOZ, uses a chimpanzee-derived cold virus to deliver Ebola virus genetic material from the Zaire strain of virus causing the outbreak in Liberia," according to a statement from NIH.
The agency said that interim results from a Phase I trial of this vaccine , which NIAID scientists co-developed with GlaxoSmithKline, "provided necessary safety information and showed that it prompted immune responses to the outer coat of Ebola virus."
Phase I trial results were similar for the other candidate, VSV-ZEBOV, NIH said, noting that this experimental vaccine "employs vesicular stomatitis virus, an animal virus that primarily affects cattle, to carry an Ebola virus gene segment."
The Public Health Agency of Canada developed the VSV-ZEBOV vaccine and licensed it to NewLink Genetics Corp., through its wholly owned subsidiary BioProtection Systems Corp.
While the Phase I results of the first experimental vaccine were published, NIH said the study results of the second candidate "were made available to the regulatory bodies reviewing the study."
"In addition to healthy adults in the general population, the trial will seek volunteers from groups at particular risk of Ebola infection, including health care workers, communities with ongoing transmission, contact tracers and members of burial teams," NIH said in a statement. "Social mobilization and community engagement activities began in Montserrado County, where the Liberian capital Monrovia is located, before the trial started and will continue in order to successfully recruit thousands of participants."
The clinical study will randomly assign a third of the volunteers to a placebo group. Remaining volunteers could receive a single injection of either the cAd3-EBOZ vaccine or the VSV-ZEBOV vaccine.
Neither volunteers nor staff will know whether a vaccine or placebo was administered as the study is double-blind, the "gold standard" in clinical research, NIH said.
"All participants will be advised on how to minimize the risk of becoming infected with Ebola virus and will be contacted by study staff about one week after the injection and then monthly for the duration of the study, which is currently expected to last about 12 months," the agency's statement continues.
With new Ebola cases in Liberia on the decline, "study investigators anticipate the need for flexibility in the conduct and design of the trial to address the changing nature of the outbreak," NIH added.
Stephen Kennedy, M.D., MPH, secretary-general of the Liberia College of Physicians and Surgeons, co-leads the study with Fatorma Baloy, Ph.D., director of Liberian Institute for Biomedical Research; and H. Clifford Lane, M.D., NIAID's deputy director for clinical research and special projects.
North Carolina-based GSK will supply the cAd3-EBOZ investigational vaccine, while the supply of the VSV-ZEBOV candidate will come from Merck, in Kenilworth, N.J., and NewLink Genetics, in Ames, Iowa.