Plymouth Meeting’s Inovio Pharmaceuticals has started a clinical study of its experimental Zika vaccine on 160 healthy adult volunteers in Puerto Rico, after the territory declared a public health emergency over the virus’s outbreak, writes Linda Loyd for the Philadelphia Inquirer.

The news gave an immediate boost to the company’s shares, which jumped by 4.63 percent to $9.27 after the announcement.

According to Inovio, the Center for Disease Control and Prevention has estimated that Zika could infect over a quarter of the Puerto Rican population by the end of this year.

Half of the volunteers in the trial will receive the vaccine with the other half getting a placebo to evaluate the safety, tolerability, and immunogenicity of the vaccine.

“The rapid progression of the Zika outbreak in Puerto Rico provides an immediate and unique opportunity to assess a preventive vaccine in a real-world setting,” said J. Joseph Kim, Inovio’s president and CEO.

He added that, if the trial is successful, the company will meet with regulators next year to decide on the most efficient path forward to develop the vaccine.

Read more about the vaccine in the Philadelphia Inquirer by clicking here.