Three vaccines offer complete protection against Zika virus in monkeys.
The results are the latest step in the quest to create a Zika vaccine that’s safe and effective for humans (SN Online: 6/28/16).
One vaccine, made with a purified, inactivated form of the virus — designated PIV — helped rhesus monkeys fend off infection from both a Zika strain from Brazil and one circulating in Puerto Rico, study coauthor Nelson Michael and colleagues report August 4 in Science. A second DNA-based vaccine that uses snippets of Zika’s genetic material to rev up the immune system was tested against a Brazilian strain. So was a third type of vaccine that relies on a virus called adenovirus to carry Zika genes into the monkeys’ bodies.
In recent days, the U.S. government and Inovio Pharmaceuticals have both started human safety trials for two other DNA-based candidates. But Michael, a vaccine researcher at the Walter Reed Army Institute of Research in Silver Spring, Md., thinks the PIV vaccine may have the best shot.
“It’s the one that’s probably going to go the distance,” he says.
DNA-based vaccines have never before been licensed for use in humans, he notes. The technique to make a PIV vaccine “goes back to Jonas Salk and polio,” Michael says. Essentially, researchers grow Zika in a lab, kill it and then purify it. “It’s a classic way to make a vaccine,” he says. “And you know what? It works.”
Human testing of the PIV vaccine will start in October. Still, Michael says evaluating many vaccine candidates is important. Any number of factors, from a bad reaction to a bankrupt manufacturer, can knock a vaccine out of the running.
“You definitely want to bet on more than one horse,” he says.