Japanese encephalitis: new options for active immunization.

Japanese encephalitis (JE) is a mosquito-borne flavivirus infection responsible for significant morbidity and mortality across Asia. Indigenous populations and those who undertake short- and long-term travel to endemic regions are at risk of infection and development of neuroinvasive disease. Effective mouse brain-derived vaccines have been available in select countries, including the United States, for decades. Limited access in Asia and safety concerns with regard to mouse brain products prompted the Chinese to develop a live, attenuated virus vaccine (SA14-14-2; Chengdu Institute of Biological Products), which has proven to be safe and efficacious following administration of >300 million doses. Recently, the portfolio of JE vaccines increased again with licensure in the United States, Europe, and Australia of a purified, inactivated virus JE vaccine (IC51; Intercell AG) and filing for licensure in Thailand and Australia of a Yellow fever-JE chimeric vaccine (ChimeriVax-JE; Sanofi Pasteur). JE is a vaccine-preventable disease with numerous options now available for active immunization. Aggressive and responsible vaccination programs should greatly diminish the burden of disease.