The First Zika Vaccines Have Been Approved for Human Testing

There’s hope. 

A team of scientists in the US and Brazil have reported the first-ever successful animal trials for two vaccine candidates for the Zika virus. With just one single injection, mice were provided with complete protection from the virus.

Now, following the promising results, the vaccines are heading into human trials.

"To the best of our knowledge, this is the first report of Zika virus vaccine protection in an animal model," Dr. Dan Barouch, from the Beth Israel Deaconess Medical Center and Harvard Medical School, said at a press conference announcing the results.

Together with colleagues at the Walter Reed Army Institute of Research (WRAIR), the researchers showed that single shots of either of two vaccines protected mice against Zika by eliciting an antibody response.

The DNA vaccines were created based on a Zika virus strain in Brazil and a purified inactivated virus (PIV) vaccine based on a strain in Puerto Rico. Further, the researchers used the same technology that WRAIR has used to successfully develop other vaccines in order to avoid the risk of licensing delays with unproven technologies.

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As reported in Nature, mice were given a single shot of one of the two vaccines, and then were exposed to Zika four weeks after vaccination. A separate group of mice was exposed to the virus eight weeks after vaccination. Both experiments had successful results, showing that the vaccines elicited an antibody response that built up an immunity to Zika.

"This critical first step has informed our ongoing work in non-human primates and gives us early confidence that development of a protective Zika virus vaccine for humans is feasible,” Col. Nelson Michael, the WRAIR Zika program co-lead, said in a press release.

However, before getting too excited, it’s important to note that there’s a chance these results may not translate over to humans.

"We need to be cautious about extrapolating the results from mice to humans," Barouch said at the press conference.

"But based on the robustness of the protection, the demonstration that antibodies protect and the similarity with other related viruses... these findings certainly raise optimism that the development of a safe and effective vaccine against Zika virus against humans may be successful."

Going forward, the researchers plan to rapidly develop the PIV vaccine, with human testing planned to begin at the WRAIR clinic before the end of the year.

The research was supported by the National Institutes of Health, Harvard, MIT, the Ragon Institute of MGH, and the Sao Paulo Research Foundation.

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