NIAID's Zika Vaccine Yields Positive Results in Human Studies

Research institutions around the world have been hard at work developing a vaccine for the Zika virus, a mosquito-borne virus that can cause devastating birth defects and has been linked with Guillain-Barré syndrome in adults. Now the results of 3 phase 1 clinical trials have shown that one candidate, an investigational Zika purified inactivated virus (ZPIV) vaccine, was well-tolerated and induced an immune response in adult participants.

The Zika virus gained its notoriety in 2016 when a startling increase in infants born with microcephaly in Brazil was linked with infection with the virus. As time progressed, further effects were also linked with the virus, prompting an urgent call for a vaccine. Many institutions are rapidly researching vaccine candidates, including investigators from the Perelman School of Medicine at the University of Pennsylvania, in partnership with investigators from the Wistar Institute, Inovio Pharmaceuticals, and GeneOne Life Science, Inc, who recently conducted a phase 1 clinical trial that showed “for the first time that humans who received up to 3 doses of a vaccine candidate produced an immune response against Zika with minimal adverse effects, opening the door to further clinical trials for this important vaccine candidate,” according to an official press release on the project.

This latest study comes from the National Institutes of Health’s National Institute of Allergy and Infectious Diseases (NIAID) and the Walter Reed Army Institute of Research (WRAIR), part of the US Department of Defense. For the double-blinded study, a total of 67 adult participants were enrolled. Of these 67 participants, a total of 55 received 2 intramuscular injections of the investigational vaccine at the same dosage each time, 4 weeks apart, while the remaining 12 participants received a placebo, at the same dosing parameters, according to a press release on the study. Blood samples were procured and tested periodically. Final results indicated that over 90% of those individuals who received the vaccine had antibodies in the blood within 4 weeks of the last dose.

The exact number of antibodies needed to protect against congenital Zika infection is not yet known; however, researchers continue to make strides in this area in animal studies.

Further research on this vaccine candidate will look at appropriate dosing, vaccine schedules, and the effects of prior immunity. “Specifically, WRAIR is examining the impact of pre-existing immunity by vaccinating participants with a yellow fever or Japanese encephalitis vaccine before beginning the ZPIV vaccine regimen,” according to the press release. “An additional study at Ponce Health Sciences University in Puerto Rico includes participants who already have been exposed naturally to a flavivirus, such as dengue. Saint Louis University seeks to identify the optimal ZPIV vaccine dose by assigning participants to receive a high, moderate or low dose, whereas Beth Israel Deaconess Medical Center is testing various dosing schedules.”

This is not the only vaccine candidate being tested by NIAID. Investigators are also working on “an experimental DNA vaccine, which is currently in Phase 2 trials at sites in the United States, Central, and South America,” according to the press release. “In addition, NIAID is helping to develop an investigational mRNA Zika vaccine and a live-attenuated vaccine candidate designed to protect against Zika and all 4 strains of dengue virus.”