What is Japanese encephalitis?
Japanese encephalitis (JE) is a serious infection caused by a virus. It occurs mainly in rural parts of Asia. JE virus spreads through the bite of infected mosquitoes. It cannot spread directly from person to person. The risk of JE is very low for most travelers, but it is higher for people living or traveling for long periods in areas where the disease is common.
Most people infected with JE virus don’t have any symptoms at all. For others, JE virus infection can cause illness ranging from fever and headache to severe encephalitis (brain infection). Symptoms of encephalitis are fever, neck stiffness, seizures, changes in consciousness, or coma.
About 1 person in 4 with encephalitis dies. Of those who don’t die, up to half may suffer permanent brain damage. There is some evidence that an infection in a pregnant woman can harm her unborn baby.
How can I prevent JE?
The best way to prevent JE is to avoid mosquito bites by:
- Remaining in well-screened areas
- Wearing clothes that cover most of your body
- Using an effective insect repellent, such as those containing DEET
- Using bed nets when accommodations are not adequately screened or air-conditioned
Some travelers to Asia should also receive JE vaccine.
Who should get JE vaccine?
Japanese encephalitis vaccine is recommended for travelers to Asia who:
- Plan to spend at least a month in areas where JE occurs
- Are traveling to these areas for less than a month but plan to visit rural areas or engage in outdoor activities
- Go to areas where there is a JE outbreak
- Are not sure of their travel plans
Laboratory workers at risk for exposure to JE virus should also get JE vaccine.
JE vaccine is approved only for people 17 years of age and older. Younger people needing protection from Japanese encephalitis should talk with their doctor.
The vaccine is given as a 2-dose series, with the doses spaced 28 days apart. The second dose should be given at least 1 week before travel.
A booster dose of JE vaccine may be given to anyone who was vaccinated more than one year ago and is still at risk of exposure, or might be re-exposed. Your doctor can give more information.
JE vaccine may be given at the same time as other vaccines.
Some people should not get JE vaccine.
- Anyone who has ever had a life-threatening allergic reaction to a previous dose of this JE vaccine should not get another dose. (Note: A different JE vaccine was available until early 2011. A life-threatening reaction to that vaccine might not be a reason to avoid the current vaccine. Ask your doctor.)
- Anyone who has a life-threatening allergy to any vaccine component should not get the vaccine. Tell your doctor if you have any severe allergies.
- Pregnant women should generally not get JE vaccine. But if you are pregnant, check with your doctor. It could be recommended under certain circumstances.
- If you will be traveling for fewer than 30 days, especially if you will be staying in major urban areas, tell your doctor. You may be at lower risk and not need the vaccine.
What are the risks from JE Vaccine?
Like any medicine, a vaccine could cause a serious reaction. But the risk of JE vaccine causing serious harm, or death, is extremely small.
- Pain or tenderness where the shot was given (about 1 person in 4)
- Redness or swelling where the shot was given (about 1 person in 20)
- Headache, muscle aches (about 1 person in 5)
Moderate or Severe Problems
Studies of this vaccine have shown severe reactions to be very rare. Like all vaccines, it will continue to be monitored for serious problems.
What if there is a severe reaction?
What should I look for?
Any unusual condition, such as a high fever or behavior changes. Signs of a severe allergic reaction can include difficulty breathing, hoarseness or wheezing, hives, paleness, weakness, a fast heart beat or dizziness.
What should I do?
- Call a doctor, or get the person to a doctor right away.
- Tell the doctor what happened, the date and time it happened, and when the vaccination was given.
- Ask your doctor to report the reaction by filing a Vaccine Adverse Event Reporting System (VAERS) form. Or you can file this report through the VAERS website at www.vaers.hhs.gov, or by calling 1-800-822-7967.
VAERS does not provide medical advice.
How can I learn more?
- Ask your doctor. They can give you the vaccine package insert or suggest other sources of information.
- Call your local or state health department.
- Contact the Centers for Disease Control and Prevention (CDC):
Vaccine Information Statement; Japanese Encephalitis Vaccine (12/7/2011)