Although there are approximately 68 flaviviruses recognized,
vaccines have been developed to control very few human flavivirus diseases. Licensed live
attenuated vaccines have been developed for
yellow fever (strain 17D) and
Japanese encephalitis (strain SA14-14-2) viruses, and
inactivated vaccines have been developed for
Japanese encephalitis and tick-borne encephalitis viruses. The
yellow fever live attenuated 17D
vaccine is one of the most efficacious and safe
vaccines developed to date and has been used to immunize more than 300 million people. A number of experimental
vaccines are being developed, most notably for
dengue. Candidate tetravalent live attenuated
dengue vaccines are undergoing clinical trials. Other
vaccines are being developed using reverse genetics,
DNA vaccines, and recombinant immunogens. In addition, the
yellow fever 17D
vaccine has been used as a backbone to generate chimeric viruses containing the premembrane and envelope
protein genes from other flaviviruses. The "
Chimerivax" platform has been used to construct chimeric
Japanese encephalitis and dengue viruses that are in different phases of development. Similar strategies are being used by other laboratories.