Japanese Encephalitis Vaccines

Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, is the leading recognized cause of childhood encephalitis in Asia. Approximately 20%–30% of patients with Japanese encephalitis (JE) die, and 30%–50% of survivors have sequelae. JEV is transmitted in Asia and parts of the Western Pacific region and residents of rural areas most often affected. Substantial progress has been made in recent decades in the prevention and control of JE due to the availability of highly effective vaccines and the implementation of JE immunization programs. However, JE remains a major public health problem in endemic areas. In addition, travelers to endemic areas are at risk of infection. Most travelers are at very low risk for JE, but some travelers are at higher risk based on their travel plans. Factors that increase the risk include traveling for a longer period, spending time in rural areas, extensive participation in outdoor activities, and staying in accommodations without air conditioning, screens, or bed nets. The three JE vaccines currently most widely available internationally are the live attenuated SA14-14-2 JE vaccine (Chengdu Institute of Biological Products [CDIBP], China), the inactivated Vero cell-derived JE vaccine (Valneva, Austria), and the live attenuated chimeric JE vaccine (Government Pharmaceutical Organization–Merieux Biological Products Co., Thailand). All three vaccines are WHO prequalified. This chapter describes JE disease and its epidemiology, and provides comprehensive information on JE vaccines.