This report updates the 1993 recommendations by CDC's Advisory Committee on Immunization Practices (ACIP) regarding the prevention of Japanese encephalitis (JE) among travelers (CDC. Inactivated Japanese encephalitis virus vaccine: recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 1993;42[No. RR-1]). This report summarizes the epidemiology of JE, describes the two JE vaccines that are licensed in the United States, and provides recommendations for their use among travelers and laboratory workers.
JE virus (JEV), a mosquito-borne flavivirus, is the most common vaccine-preventable cause of encephalitis in Asia. JE occurs throughout most of Asia and parts of the western Pacific. Among an estimated 35,000--50,000 annual cases, 20%--30% of patients die, and 30%--50% of survivors have neurologic or psychiatric sequelae. No treatment exists. For most travelers to Asia, the risk for JE is very low but varies on the basis of destination, duration, season, and activities.
JE vaccine is recommended for travelers who plan to spend a month or longer in endemic areas during the JEV transmission season and for laboratory workers with a potential for exposure to infectious JEV. JE vaccine should be considered for 1) short-term (<1 month) travelers to endemic areas during the JEV transmission season if they plan to travel outside of an urban area and will have an increased risk for JEV exposure; 2) travelers to an area with an ongoing JE outbreak; and 3) travelers to endemic areas who are uncertain of specific destinations, activities, or duration of travel. JE vaccine is not recommended for short-term travelers whose visit will be restricted to urban areas or times outside of a well-defined JEV transmission season.
Two JE vaccines are licensed in the United States. An inactivated mouse brain--derived JE vaccine (JE-VAX [JE-MB]) has been licensed since 1992 to prevent JE in persons aged ≥1 year traveling to JE-endemic countries. Supplies of this vaccine are limited because production has ceased. In March 2009, an inactivated Vero cell culture-derived vaccine (IXIARO [JE-VC]) was licensed for use in persons aged ≥17 years. JE-MB is the only JE vaccine available for use in children aged 1−16 years, and remaining supplies will be reserved for use in this group.

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