Plymouth Meeting’s Inovio Pharmaceuticals has enrolled 160 healthy adult volunteers in Puerto Rico for a clinical study of its experimental Zika vaccine, writes Linda Loyd for Philly.com.

Earlier this year, the company received positive results from a similar Zika clinical trial on humans. These were done at various Northern American locations including Philadelphia.

After them, the company said three doses of the vaccine had generated a strong antibody response in all of the volunteers with minimal side effects.

The company chose Puerto Rico for its latest trial following an outbreak of the deadly virus there. The results are expected within a year. However, in order to gain FDA approval for the vaccine, Inovio still has to complete another study.

For this one, volunteers will be given the vaccine before being exposed to the Zika virus. This will determine if the antibody response is strong enough to prevent infection.

“We will have to get into an area where there’s active infection going on,” said Scott White, vice president of clinical development. This will “prove that the antibody response is strong enough to protect them.”

Read more about Inovio’s Zika trial at Philly.com by clicking here.