What is Japanese encephalitis?
Japanese encephalitis (JE) is a serious infection caused by the Japanese encephalitis virus.
- It occurs mainly in rural parts of Asia.
- It is spread through the bite of an infected mosquito. It does not spread from person to person.
- Risk is very low for most travelers. It is higher for people living in areas where the disease is common, or for people traveling there for long periods of time.
- Most people infected with JE virus don't have any symptoms. Others might have symptoms as mild as a fever and headache, or as serious as encephalitis (brain infection).
- A person with encephalitis can experience fever, neck stiffness, seizures, and coma. About 1 person in 4 with encephalitis dies. Up to half of those who don't die have permanent disability.
- It is believed that infection in a pregnant woman could harm her unborn baby.
JE vaccine can help protect travelers from JE disease.
Who should get JE vaccine and when?
Japanese encephalitis vaccine is approved for people 2 months of age and older. It is recommended for travelers to Asia who:
- plan to spend at least a month in areas where JE occurs,
- plan to travel for less than a month, but will visit rural areas and spend a lot of time outdoors,
- travel to areas where there is a JE outbreak, or
- are not sure of their travel plans.
Laboratory workers at risk for exposure to JE virus should also be vaccinated. The vaccine is given as a 2-dose series, with the doses spaced 28 days apart. The second dose should be given at least a week before travel. Children younger than 3 years of age get a smaller dose than patients who are 3 or older.
A booster dose might be recommended for anyone 17 or older who was vaccinated more than a year ago and is still at risk of exposure. There is no information yet on the need for a booster dose for children.
NOTE:The best way to prevent JE is to avoid mosquito bites. Your doctor can advise you.
Who should not get JE vaccine or should wait?
- Anyone who has had a severe (life-threatening) allergic reaction to a dose of JE vaccine should not get another dose.
- Anyone who has a severe (life threatening) allergy to any component of JE vaccine should not get the vaccine.Tell your doctor if you have any severe allergies.
- Pregnant women should usually not get JE vaccine. If you are pregnant, check with your doctor. If you will be traveling for fewer than 30 days, especially if you will be staying in urban areas, tell your doctor. You might not need the vaccine.
What are the risks from JE vaccine?
With a vaccine, like any medicine, there is a chance of side effects. When side effects happen, they are usually mild and go away on their own.
- Pain, tenderness, redness, or swelling where the shot was given (about 1 person in 4).
- Fever (mainly in children).
- Headache, muscle aches (mainly in adults).
Moderate or Severe problems
- Studies have shown that severe reactions to JE vaccine are very rare.
Problems that can happen after any vaccine
- Brief fainting spells can happen after any medical procedure, including vaccination. Sitting or lying down for about 15 minutes can help prevent fainting, and injuries caused by a fall. Tell your doctor if you feel dizzy, or have vision changes or ringing in the ears.
- Lasting shoulder pain and reduced range of motion in the arm where the shot was given can happen, very rarely, after a vaccination.
- Severe allergic reactions from a vaccine are very rare, estimated at less than 1 in a million doses. If one were to occur, it would usually be within a few minutes to a few hours after the vaccination.
The safety of vaccines is always being monitored. For more information, visit: Web Site.
What if there is a serious reaction?
What should I look for?
- Look for anything that concerns you, such as signs of a severe allergic reaction, very high fever, or behavior changes. Signs of a severe allergic reaction can include hives, swelling of the face and throat, difficulty breathing, a fast heartbeat, dizziness, and weakness. These would usually start a few minutes to a few hours after the vaccination.
What should I do?
- If you think it is a severe allergic reaction or other emergency that can't wait, call 9-1-1 or get the person to the nearest hospital. Otherwise, call your doctor.
- Afterward, the reaction should be reported to the ''Vaccine Adverse Event Reporting System'' (VAERS). Your doctor might file this report, or you can do it yourself through the VAERS web site at Web Site, or by calling1-800-822-7967.
VAERS is only for reporting reactions. They do not give medical advice.
How can I learn more?
- Ask your doctor.
- Call your local or state health department.
- Contact the Centers for Disease Control and Prevention (CDC): Call1-800-232-4636(1-800-CDC-INFO), visit the CDC's travelers' health website at Web Site, or visit CDC's JE website at Web Site.
Japanese Encephalitis Vaccine Information Statement. U.S. Department of Health and Human Services/Centers for Disease Control and Prevention National Immunization Program. 01/24/2014.
AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Selected Revisions: March 15, 2015.