Experimental Zika virus vaccines protect against congenital damage
Two experimental vaccines have been found to restrict Zika virus transmission from pregnant mice to their fetuses and prevent damage to the placenta and fetal demise.
Scientists from the National Institutes of Health, Washington University School of Medicine in St. Louis and the University of Texas Medical Branch tested a live-attenuated vaccine candidate and an mRNA vaccine candidate.
Currently, no vaccine or treatment is available to prevent or treat Zika virus disease or congential Zika syndrome. Several vaccine candidates have, however, advanced to clinical trials in humans.
The current study is the first animal study to demonstrate protection from experimental vaccines before the animal becomes pregnant.
Researchers gave a group of non-pregnant female mice two injections of the mRNA vaccine 28 days apart; another group received a placebo.
A third group of non-pregnant female mice received a single dose of the live-attenuated vaccine, and another control group received a placebo.
Tests revealed that mice that received the experimental vaccines produced high levels of neutralizing antibodies against Zika virus in their blood.
The mice were then mated and infected with Zika.
Most fetuses in the vaccinated mice showed no evidence of having Zika virus. Those mice that were infected showed diminished levels of the virus RNA in maternal, placental and fetal tissues, resulting in protection against placental damage and fetal demise.
“Together the data show that both experimental vaccines can restrict in utero transmission of Zika virus in mice,” according to the researchers. “Further evaluation of the experimental vaccines is warranted as a vaccine that prevents congenital Zika syndrome in people is a critical public health need.”