New vaccines for Japanese encephalitis.

Epidemics of encephalitis occurring throughout much of Asia are caused by Japanese encephalitis virus (JEV), a flavivirus maintained in a zoonotic cycle and transmitted by the mosquito, Culex tritaeniorhynchus. Resident populations, including short-or long-term visitors to enzootic regions, are at risk for Japanese encephalitis (JE) infection and disease. For the past several decades, effective killed viral vaccines prepared in tissue culture or mouse brain have been used to immunize travelers and residents of affected countries. Cost, efficacy, and safety concerns led to the development of a single-dose live attenuated virus vaccine (SA14-14-2) and more recently, to the licensure in the United States, Europe, and Australia of a purified inactivated, tissue culture-based JE vaccine (IC51; Intercell AG, Vienna, Austria) and the soon-to-be-licensed live-attenuated yellow fever-JE chimeric vaccine (ChimeriVax-JE; Sanofi Pasteur, Lyon, France). Safe and effective JE vaccines are now available to the entire at-risk population and should greatly diminish the burden of disease.