Results from a large randomised, placebo-controlled clinical trial in Liberia show that two candidate Ebola vaccines pose no major safety concerns and can elicit immune responses by one month after initial vaccination that last for at least one year. "The work of PREVAIL, ranging from the Ebola vaccine to the Ebola survivor studies, clearly manifest the prospects of such a sustainable partnership and clinical research platform". PREVAIL operates under the umbrella of a Joint Liberia-U.S.
First launched in February 2015, the first study, called PREVAIL 1, was originally created to enroll 28,000 volunteers.
One group received one test vaccine, the second group the other test vaccine, and the third group received a placebo (saltwater injection). Each participant provided blood samples prior to their vaccinations, and again at one-week, one-month, six-month, and one-year intervals following vaccination.
The researchers then used their samples to test for antibodies associated with the Ebola virus. At one week, researchers documented "modest" responses that ended up growing significantly by the one-month point, according to a new release. However, by one month, 71 percent of cAd3-EBOZ recipients and 84 percent of rVSV-ZEBOV recipients developed an antibody response compared with three percent of placebo recipients.
The findings are based on a study of 1,500 adults that began during the West Africa Ebola outbreak.
At one year, the antibody responses were largely maintained in both groups: 64 percent of cAd3-EBOZ recipients and 80 percent of rVSV-ZEBOV recipients had antibody response compared with seven percent of placebo recipients.
Some participants who received the investigational vaccines experienced mild to moderate side effects that resolved, such as a headache, muscle pain, feverishness and fatigue. Overall, investigators did not identify any major safety concerns related to the vaccines. "To each and every one of them, we extend our deep gratitude".
PREVAIL conducts collaborative biomedical research in accordance with best practices, to advance science, strengthen health policy and practice, and improve the health of Liberians and people worldwide.
"We can not succeed in the fight against Ebola unless we identify primary prevention tools".
The PREVAIL I study will continue to follow for several years those who had enrolled into the study to determine the long term benefits of the vaccines. The National Institute for Allergy and Infectious Diseases (NIAID) sponsored the study while GSK and Merck provided vaccine doses.
The cAd3-EBOZ vaccine candidate was co-developed by NIAID's Vaccine Research Center and GlaxoSmithKline (GSK), while rVSV-ZEBOV, initially engineered by scientists from the Public Health Agency of Canada, is now licensed to Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., (Merck).
Before that study, Merck's vaccine posted 100% efficacy in a novel "ring study" that didn't incorporate a placebo arm.
NIAID noted that at the beginning of the trial, the researchers found that 4 percent of participants already developed a small threshold of Ebola antibodies, which indicated past infection but had no known history of Ebola virus disease.