Introduction
Class Name(s):
Brand Name(s):
Why get vaccinated?
Japanese encephalitis vaccine may prevent encephalitis (infection of the brain) that can occur after infection with Japanese encephalitis virus (JEV). The virus is carried by mosquitos, primarily in Asia and the western Pacific countries.
Encephalitis from JEV infection can cause headache, fever, altered mental state, seizures, and coma.
Japanese encephalitis vaccine does not contain active virus. It works by triggering the body to create antibodies to the virus to protect against potential infection.
How is the vaccine given?
Japanese encephalitis vaccine comes as a suspension to be given intramuscularly (into a muscle) by a healthcare provider.
Japanese encephalitis vaccine is given as two doses 28 days apart (some adults may receive the doses 7 days apart). You should receive both doses at least one week prior to potential exposure. A booster dose (3rd dose) may be given at least 11 months after completion of the first two doses if exposure to JEV continues to be expected.
What should you tell the person who is giving the vaccine?
Tell your vaccine provider if you:
In some cases, your health care provider may decide to postpone vaccination to a future visit.
What are the risks from vaccination?
Side effects that have been reported with Japanese encephalitis vaccine include:
Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately or get emergency medical treatment:
People sometimes faint after medical procedures, including vaccination. Tell your provider if you feel dizzy or have vision changes or ringing in the ears.
Adverse reactions should be reported to the Vaccine Adverse Event Reporting System (VAERS). Your health care provider will usually file this report, or you can do it yourself. Visit http://vaers.hhs.gov or call 1-800-822-7967. VAERS is only for reporting reactions, and VAERS staff members do not give medical advice.
How can I learn more?
This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.
The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.
AHFS® Patient Medication Information™ Copyright, 2026. The American Society of Health-System Pharmacists®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Selected Revisions: July 15, 2026.