FDA approves the first vaccine for dengue fever, but with major restrictions

https://www.statnews.com/2019/05/01/fda-dengue-vaccine-restrictions/

FDA approves the first vaccine for dengue fever, but with major restrictions

By Helen Branswell @HelenBranswell

May 1, 2019

The Food and Drug Administration on Wednesday approved the first vaccine against dengue fever, one that protects against a common disease but has generated significant controversy due to evidence it can increase the risk of severe infection in some people.

The agency ruled that Dengvaxia, manufactured by Sanofi Pasteur, can only be used in individuals aged 9 to 16 living in parts of the United States where the dengue virus is endemic — in other words, where it circulates on an ongoing basis. Dengue is found only in Puerto Rico and a few other U.S. offshore territories and protectorates.

Furthermore, the vaccine can only be given to children and teens who have had one previous laboratory-confirmed case of dengue.
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Regulators have sought to restrict access to Dengvaxia following post-marketing research by Sanofi that showed that, while the vaccine offers protection for people who have already had at least one bout of dengue, it increases the risk of severe infection in children who were dengue-naïve — that is, never infected — when they were vaccinated.

There are four serotypes of dengue viruses, numbered 1 through 4. Infection with one virus does not protect against the others and actually appears, for a time, to increase the risk that another dengue infection will trigger a severe form of the disease that can be life threatening. That phenomenon is called antibody-dependent enhancement, or ADE.

After Sanofi announced its findings, the Philippines — the only country to have used the vaccine broadly to date — suspended use of Dengvaxia and ultimately revoked its license. Prosecutors have charged Sanofi, a half-dozen of its employees, and several current and former Philippines health officials over a series of deaths it alleges are linked to use of the vaccine.
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