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New Vaccine Offers Some Protection Against Dengue

WebMD Health News
Reviewed by Louise Chang, MD

Sept. 10, 2012 -- A new study shows that an experimental vaccine appears to offer good protection against three of the four viruses that cause dengue fever.

If further studies confirm the findings, researchers say the new vaccine would be the first to fight the painful and sometimes deadly disease, which strikes more than 100 million people around the world each year.

Dengue viruses are carried by mosquitoes. They cause a high fever, severe headache, and muscle and joint pain. They also make people bleed more easily than normal. Infected people may bleed from the nose or gums, or they may bruise easily. Young children tend to get more severe cases than adults.

Dengue mostly strikes people in tropical areas. So it’s largely been seen as a disease that has plagued developing countries. But in 2009, the illness popped up again in the U.S., infecting 90 people in southern Florida. It was the first time dengue fever had been seen in that state since 1934.

A New Vaccine, Decades in the Making

The new vaccine was tested in 4,000 school children in Thailand. The children got either three doses of vaccine or placebo shots spread six months apart. The vaccine was meant to spur immunity to all four of the viruses that cause dengue fever.

After two years, the number of dengue cases was virtually the same between the vaccine and comparison groups. That might have spelled failure for the vaccine, which had been decades in the making. But researchers got lucky. They happened to be testing their vaccine during what turned out to be a dengue epidemic.

“The high number of cases identified allowed us to look at [effectiveness] by [virus strain],” says Derek Wallace, MD, regional director of clinical development for Sanofi Pasteur in Singapore.

What they found was that vaccine offered 60% to 90% protection against three of the four dengue strains. The vaccine didn’t seem to work against the virus responsible for most of the cases in the outbreak: DENV2.

Vaccine Is ‘Two Steps Forward, One Step Back’

Wallace says his team is still trying to figure out why the vaccine didn’t protect against DENV2.

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