FORT COLLINS — Inviragen, a life-science company, said Wednesday it reached a "milestone" in a study on its dengue virus vaccine.

As a result, the company will start the second stage of a Phase 2 clinical trial on the vaccine DENVax, which will undergo safety testing in children.

Inviragen begins the second stage testing following review by an independent group of the first stage in the study.

The completion of the first stage of the Phase 2 study marks an important milestone for Inviragen, CEO Dan Stinchcomb said in a statement.

"It represents the first comprehensive safety evaluation of the vaccine in individuals of various ages who live in dengue-endemic areas," Stinchcomb said. That evaluation "determined that the first dose of the vaccine is well tolerated in adults, adolescents and children, some of whom were pre-exposed to dengue viruses."

More than 300 people received the vaccine during clinical trials, said Dr. Gilad Gordon, Inviragen's chief medical officer.

"Overall, DENVax has been very well tolerated with mostly mild adverse events," he said. "The second part of this Phase 2 clinical trial will yield additional insight about the vaccine's safety and immunogenicity in children as young as 18 months and will set the stage for future vaccine efficacy studies."

DENVax, invented by scientists at the Centers for Disease Control and Prevention in Fort Collins, is designed to protect against all four strains of dengue fever, which is spread by mosquitoes in tropical regions. As many as 100 million people are affected annually, according to the CDC.

Established in 2005, Inviragen has offices in Wisconsin and Singapore.