HealthDay News—An experimental DNA-based vaccine for Zika virus has proceeded to human safety trials, according to findings published online September 22 in Science.

To test the potential effectiveness of the Zika vaccine, researchers provided a single dose to 6 rhesus monkeys and 2 doses to 18 monkeys.

None of the monkeys that received a single dose were protected from Zika infection, but the vaccine did appear to create an antibody response, the researchers found. Their blood contained less Zika virus than animals who did not receive the vaccine. The 2-dose vaccine series protected 17 out of the 18 monkeys against exposure to Zika, and provided researchers with an idea of how much antibody response is needed to protect against infection.

“These data not only indicate DNA vaccination could be a successful approach to protect against Zika virus infection, but also suggest a protective threshold of vaccine-induced neutralizing activity that will prevent viremia following acute infection,” the authors write. Based on these findings, clinical safety trials in healthy humans have begun.

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Dowd KA, Ko S-Y, Morabito KM, et al. Rapid development of a DNA vaccine for Zika virus. Science. 2016. doi: 10.1126/science.aai9137