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Japanese Encephalitis

What is it?

Japanese encephalitis is a virus spread by mosquitoes. This virus is related to dengue and yellow fever

Although most people who are infected with Japanese encephalitis are asymptomatic, it is still a dangerous disease. The symptoms of Japanese encephalitis are headache, fever, vomiting, seizures, and encephalitis (brain swelling), which can be deadly.

This vaccine is not recommended as a routine vaccine (in the US), but it may be recommended if you are traveling to a location with Japanese encephalitis. 

Areas With Japanese Encephalitis

  Map from the World      Health Organization

Vaccine Information:

Active Ingredients:

This vaccine uses inactivated Japanese Encephalitis virus as the active ingredient.

Note: there may be trace amounts of DNA and proteins from the cells used to grow the virus for this vaccine.

Inctive Ingredients:
Ingredient amounts based on a 0.5mL dose


  • Asymptomatic: does not have symptoms or does not appear sick

  • Encephalitis: Inflammation (swelling) of the brain

  • Seizures: A sudden burst of electrical activity in the brain that can affect movement and behavior

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Last updated: Feb. 12, 2023

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