The U.S. government has launched its first clinical trial of a Zika vaccine in humans, the National Institutes of Health (NIH) said Wednesday.
The early-stage study, led by the NIH's National Institute of Allergy and Infectious Diseases (NIAID), will evaluate the experimental vaccine's safety and ability to generate an immune system response in participants.
The vaccine will be tested in at least 80 healthy volunteers, aged 18 to 35, at three sites -- the NIH Clinical Center in Bethesda, Maryland, the University of Maryland in Baltimore and Emory University in Atlanta.
NIAID Director Anthony Fauci said that his agency has worked expeditiously to ready the vaccine, which has been shown to be "very encouraging" in animal testing.
"We are pleased that we are now able to proceed with this initial study in people," Fauci said in a statement.
"Although it will take some time before a vaccine against Zika is commercially available, the launch of this study is an important step forward."
The vaccine is similar to an investigational West Nile vaccine developed by the NIAID, which was found to be safe and induced an immune response when tested in an early-stage clinical trial.
It includes a small, circular piece of DNA, called a plasmid, that scientists engineered to contain genes that code for proteins of the Zika virus, the NIH said.
When the vaccine is injected into the arm muscle, cells read the genes and make Zika virus proteins, which self-assemble into virus-like particles to induce an immune response.
Such DNA vaccines do not contain infectious material, so they cannot cause a vaccinated individual to become infected with Zika and have been shown to be safe in previous clinical trials for other diseases.
Volunteers will be divided randomly into four study groups of 20 people each, and all will first receive a vaccination via a needle-free injector.
Half of the participants will receive one additional vaccination eight weeks or 12 weeks later. The remaining participants will receive two additional vaccinations: one group will receive a second vaccine at week four and a third at week eight; the other group will receive a second vaccine at week four and a third at week 20.
Initial safety and immunogenicity data from the trial are expected by January 2017.
If results show a favorable safety profile and immune response, a larger trial could begin in early 2017 in Zika-endemic countries, the NIH said.
So far, there are no vaccines or specific therapeutics to prevent or treat Zika virus disease.
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