There is only one approved vaccine for dengue. It has been licensed in six countries and several others are considering how to use it. Although the disease is rare in the continental United States, dengue is seen in Puerto Rico, Latin America, Southeast Asia and the Pacific Islands.
Spread by mosquitoes, dengue fever often causes a mild first infection, but a second one is typically more severe and potentially fatal. There is concern that if a vaccine fails to fully protect people, it could increase the risk of making them sick instead of keeping them well.
Researchers reanalyzed data from dengue vaccine trials with more than 30,000 people in 10 countries.
The studies found that while the vaccine can reduce illness and hospitalization by up to 30 percent in places with high dengue transmission, it could significantly increase illness and hospitalization in regions with low transmission of the virus.
"In vaccines, you hope for more than 30 percent success, but it's the only vaccine available right now to slow dengue," said co-lead author Dr. Isabel Rodriguez-Barraquer. She is a research associate at Johns Hopkins University's Bloomberg School of Public Health.
"If this vaccine is used correctly, many people could be spared illness and hospitalization from dengue. But we should make sure we only use it in places where our data suggest it will do more good than harm," she said in a university news release.
Partly due to these findings, the World Health Organization recommends that the vaccine be used only where there is high dengue transmission.
"We should be careful in considering where and how to use this vaccine as there is still uncertainty about its impact," study co-author Derek Cummings said in the news release. Cummings is a professor of biology at the University of Florida and an adjunct professor at the Bloomberg School.
The study is published Sept. 2 in Science.
The U.S. Centers for Disease Control and Prevention has more on dengue.
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