Two experimental Zika virus DNA vaccines developed by National Institutes of Health (NIH) scientists protected monkeys against Zika infection after two doses, according to a study published in Science. One of those vaccines is being evaluated in a Phase 1 human trial now under way in three U.S. locations to evaluate the vaccine’s safety and ability to generate immune responses in people.
Most Zika infections are asymptomatic or cause a mild illness lasting about a week. In addition, Zika virus infection during pregnancy can affect the fetus and lead to serious birth defects, especially those involving the developing brain. There are no vaccines or specific therapeutics to prevent or treat Zika virus disease.
Scientists from the Vaccine Research Center within NIH’s National Institute of Allergy and Infectious Diseases (NIAID) developed the experimental vaccines using circular DNA engineered to produce a particle mimicking the shape of the Zika virus. The experimental vaccines, which do not contain infectious material and thus cannot cause Zika infection, are similar to a vaccine the researchers have tested against West Nile virus--part of the same virus family as Zika.
In their study, the researchers vaccinated groups of rhesus macaques using the two different experimental Zika DNA vaccines in different doses. They then exposed the monkeys to an infectious dose of Zika virus. Both experimental vaccines were highly effective when given in two doses. One of the vaccines (VRC5288) is being tested in a Phase 1 clinical trial under way in volunteers in Bethesda, Maryland, Baltimore and Atlanta. If the Phase 1 results are favorable, NIAID plans to initiate a Phase 2 trial in Zika-endemic countries in early 2017. The second vaccine (VRC5283) is awaiting a Phase 1 clinical trial start date.