Why can't the dengue vaccine Dengvaxia be used in people who haven't already had dengue?

The dengue vaccine Dengvaxia appears to act like a first dengue infection, which typically results in either no symptoms or a mild illness. Any subsequent infection can lead to severe dengue, including dengue hemorrhagic fever (DHF), a more severe form of the disease that can be fatal.

People who have not been previously infected by dengue virus should not have the dengue vaccine. The vaccine is intended to protect people who have already been infected with dengue virus from further infection and the development of the more severe form of dengue disease.

Dengvaxia (dengue tetravalent vaccine, live) was approved by the FDA on May 1, 2019 for the prevention of dengue caused by dengue virus serotypes 1, 2, 3 and 4 in people 9 years through 16 years of age living in endemic areas who have laboratory-confirmed previous dengue infection. Endemic areas in the U.S. include the territories of American Samoa, Guam, Puerto Rico and the U.S. Virgin Islands.

There are several different serotypes of the dengue virus, including dengue types 1,2,3 and 4. Once someone has had one type of dengue, they only become immune to that type, so they can still become infected with the other types. Those who have been infected before, and are infected with dengue a second, third or fourth time are at a much higher risk of severe dengue disease.

Dengvaxia is a live, attenuated vaccine that is administered as three separate injections, with the initial dose followed by two additional shots given six and twelve months later.

Commonly reported side effects include headache, muscle pain, joint pain, fatigue, injection site pain and low-grade fever.