Experimental Zika virus vaccine shows promise

Recent tests of an experimental Zika virus vaccine in rhesus macaques, a primate, show the vaccine lowered levels of virus in pregnant monkeys and improved fetal outcomes, according to a new study in Science Translational Medicine.

Zika is transmitted via mosquitoes and through sex. It causes severe birth defects in babies whose mothers become infected during pregnancy. In 2015 and 2016, Zika virus outbreaks caused thousands of cases of congenital Zika syndrome.

The vaccine contains a small circular piece of DNA with genes encoded with the Zika virus surface proteins. Researchers compared 12 unvaccinated pregnant macaques and 13 macaques vaccinated before pregnancy.

The macaques were exposed to the virus three times during the first and second trimesters. The vaccinated group had a significantly lower amount of the virus in their blood and were considerably less likely to transmit the virus to the fetus. The virus was also detectable for a shorter timeframe.

An immune response that prevents infection entirely with no detectable virus may not be necessary for significant protection, the researchers found.

The vaccine is under evaluation for a human clinical trial. It would need to be given to adolescents and adults of childbearing age before pregnancy.

Researchers included the National Institute of Allergy and Infectious Diseases.