NIH Begins Testing Investigational Zika Vaccine in Humans

NIAID recently launched a clinical trial of a vaccine candidate intended to prevent Zika virus infection.

Photo: NIAID

NIAID has launched a clinical trial of a vaccine candidate intended to prevent Zika virus infection. The early stage study will evaluate the experimental vaccine’s safety and ability to generate an immune system response in participants. At least 80 healthy volunteers ages 18-35 years at 3 study sites in the United States, including the Clinical Center, are expected to participate in the trial. Scientists at NIAID’s Vaccine Research Center developed the investigational vaccine—called the NIAID Zika virus investigational DNA vaccine—earlier this year.

The study is part of the U.S. government response to the ongoing outbreak of Zika virus in the Americas. According to the Centers for Disease Control and Prevention, more than 50 countries and territories have active Zika virus transmission. In the U.S. and its territories, more than 6,400 Zika cases have been reported.  

Although Zika infections are usually asymptomatic, some people experience mild illness lasting about a week. However, Zika virus infection during pregnancy can cause a serious birth defect called microcephaly, as well as other severe fetal defects of the brain and other organs. There are no vaccines or specific therapeutics to prevent or treat Zika virus disease.

The NIAID Zika virus investigational DNA vaccine approach is similar to that used for another investigational vaccine developed by NIAID for West Nile virus. That vaccine candidate was found to be safe and induced an immune response when tested in a phase 1 clinical trial.

The investigational Zika vaccine includes a small, circular piece of DNA—called a plasmid—that scientists engineered to contain genes that code for proteins of the Zika virus. 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. The body mounts an immune response to these particles, including neutralizing antibodies and T cells. 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.