The Food and Drug Administration has approved the first vaccine for dengue, Dengvaxia, but placed significant restrictions on its use because the vaccine has been shown to put some people at heightened risk for a severe form of the disease.

In clearing the vaccine, the agency acknowledged the serious public health benefit of slowing a disease that affects hundreds of millions of people around the world. The decision may also help a struggling product whose use has stalled because of concerns over its possible risks.

“It tells the world that if properly used, the vaccine can be effective,” said Duane Gubler, an emeritus professor at Duke-NUS Medical School who is one of the inventors of a competing dengue vaccine made by Takeda, and has consulted in the past for Sanofi, which makes Dengvaxia.

Sanofi has sold Dengvaxia overseas since 2015, but the vaccine hit a major roadblock in 2017 after the Philippines, which had widely distributed the product to schoolchildren, halted its use and revoked Sanofi’s license.