Clinical Update
Updated Recommendations to Prevent Japanese Encephalitis in Travelers

In July 2019, the Advisory Committee on Immunization Practices (ACIP) published updated recommendations regarding prevention of Japanese encephalitis (JE) among US travelers.

JE virus spreads to travelers through mosquito bites and is a risk throughout most of Asia and parts of the western Pacific (see risk areas and transmission season). Although most travelers are at very low risk of disease, some may be at a greater risk because of their travel plans. Factors that increase a traveler’s risk of exposure include

  • Travel in risk areas for prolonged periods
  • Travel during the JE transmission season
  • Spending time in rural areas
  • Participating in outdoor activities (such as hiking or camping) that increase the risk of exposure to the mosquitoes that spread JE
  • Staying in accommodations that lack air conditioning, window and door screens, or bed nets, thereby increasing the risk of exposure to infected mosquitoes

Most people infected with the JE virus do not have symptoms or have only mild symptoms. However, a small percentage of people develop brain inflammation with symptoms of headache, fever, convulsions, and coma. This can be fatal or have serious long-term consequences.

One JE vaccine (Ixiaro) is licensed in the United States to prevent infection in people aged 2 months or older. ACIP recommends Ixiaro for people moving to risk areas to live, longer-term (for example, 1 month or longer) travelers to risk areas, and frequent travelers to risk areas. Consider vaccination for shorter-term travelers (for example, less than 1 month) at increased risk of exposure to JE based on the risk factors listed above. Also consider vaccination for travelers not sure about their exact duration of travel, destinations, or activities.

ACIP does not recommend vaccination for travelers with low-risk itineraries, such as shorter-term travel limited to urban areas or travel that occurs outside the JE transmission season.

Ixiaro is given as a two-dose series, with doses spaced 28 days apart. Adults aged 18–65 years can get the second dose as early as 7 days after the first. Give the second dose at least 1 week before travel. Administer a booster dose at least 1 year after completion of the primary series to travelers who remain at risk for JE infection.

All travelers should also take steps to prevent insect bites to prevent JE as well as other infections transmitted by insects.

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