For the first time, researchers will be allowed to test an experimental Zika vaccine on humans. The Food and Drug Administration has approved a clinical trial that will determine if a Zika vaccine is safe to use on healthy humans, STAT reports. If the trial is successful, researchers will conduct tests on humans who are infected with the virus in later trials.

Testing for safety and tolerability

The trial will begin in a few weeks, according to a press release published by Inovio Pharmaceuticals, one of the two companies behind the vaccine. Researchers will inject the vaccine — called GLS-5700 — into 40 healthy people to evaluate how well it's tolerated. The company should be able to report results from the trial later this year.

Testing a vaccine on people who are healthy is standard for human drug trials. If it seems safe, researchers will conduct trials involving people who actually have the virus. That means that this first trial won't actually be able to determine if the vaccine works. When Inovio tested the vaccine on large animals, it caused a strong antibody response, the company says.