Japanese Encephalitis Virus Vaccine (Inactivated)

Name: Japanese Encephalitis Virus Vaccine (Inactivated)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Suspension, Intramuscular:

Ixiaro: (0.5 mL) [latex free; contains albumin bovine, protamine sulfate, sodium metabisulfite]

Brand Names U.S.

  • Ixiaro


This vaccine induces antibodies to neutralize the Japanese encephalitis virus. Antibody response is measured using a 50% plaque-reduction neutralization antibody test (PRNT50); a threshold of ≥1:10 is considered protective immunity.

Onset of Action

Protective immunity was observed in ~21% of adults 10 days after the first vaccine dose and in 96% to 100% of children and adults 28 days after the second vaccine dose.

Use Labeled Indications

Japanese encephalitis prevention: Active immunization against Japanese encephalitis (JE) for persons 2 months of age and older

The Advisory Committee on Immunization Practices (ACIP) recommends vaccination for (CDC [Fischer 2010]; CDC 2013):

- Persons spending ≥1 month in endemic areas during transmission season

- Research laboratory workers who may be exposed to the Japanese encephalitis virus

Vaccination should also be considered for the following:

• Travelers to areas with an ongoing outbreak

• Travelers spending <30 days in endemic areas during the transmission season and planning to go outside of urban areas and have an increased risk of exposure. For example, high-risk activities include extensive outdoor activity in rural areas especially at night; extensive outdoor activities such as camping, hiking, etc; staying in accommodations without air conditioning, screens or bed nets.

• Travelers to endemic areas who are unsure of specific destination, activities, or duration of travel

Japanese encephalitis vaccine is not recommended for short-term travelers whose visit will be restricted to urban areas or periods outside of the well-defined JE virus transmission season.

Dosing Adult

Primary immunization: IM: 0.5 mL/dose; a total of 2 doses given on days 0 and 28. Series should be completed at least 1 week prior to potential exposure.

Booster dose: Booster dose may be given prior to potential re-exposure if the primary series was completed >1 year previously.

Note: If the second dose is missed, limited data from one clinical trial in adults demonstrate a 99% seroconversion rate when the second dose was administered 11 months after the initial dose.

Dosing Geriatric

Refer to adult dosing.


For IM injection. Do not inject IV, SubQ, or intradermally. Shake well prior to use to form a homogeneous suspension. Do not use if discolored or if particulate matter remains. Do not mix with other vaccines or injections; separate needles and syringes should be used for each injection (ACIP [Kroger 2017]).

When administering to children 2 to 11 months of age, the preferred site for administration is the anterolateral aspect of the thigh; for children 1 to <3 years of age, the anterolateral aspect of the thigh or deltoid muscle may be used (if mass is adequate); the deltoid muscle is the preferred site in children ≥3 years, adolescents, and adults. To prevent syncope related injuries, adolescents and adults should be vaccinated while seated or lying down (ACIP [Kroger 2017]).

Ixiaro is available only in a prefilled syringe containing 0.5 mL. In order to administer a 0.25 mL dose in children 2 months to <3 years, first shake the syringe to form a homogenous suspension. Attach a sterile needle to the prefilled syringe and while holding the syringe upright, discard 0.25 mL of the suspension. Attach a new sterile needle prior to administration.

Canadian labeling recommends avoiding IM administration in patients with bleeding disorders (eg, thrombocytopenia, hemophilia) and suggests that SubQ administration may be considered in these patients. Clinical efficacy data regarding this route is lacking and the U.S. labeling does not recommend SubQ administration. For patients at risk of hemorrhage following intramuscular injection, the vaccine should be administered intramuscularly if, in the opinion of the physician familiar with the patient's bleeding risk, the vaccine can be administered by this route with reasonable safety. If the patient receives antihemophilia or other similar therapy, intramuscular vaccination can be scheduled shortly after such therapy is administered. A fine needle (23 gauge or smaller) can be used for the vaccination and firm pressure applied to the site (without rubbing) for at least 2 minutes. The patient should be instructed concerning the risk of hematoma from the injection. Patients on anticoagulant therapy should be considered to have the same bleeding risks and treated as those with clotting factor disorders (ACIP [Kroger 2017]).

Drug Interactions

Belimumab: May diminish the therapeutic effect of Vaccines (Inactivated). Management: Patients should receive inactivated vaccines prior to initiation of belimumab therapy whenever possible, due to the risk for an impaired response to the vaccine during belimumab therapy. Consider therapy modification

Fingolimod: May diminish the therapeutic effect of Vaccines (Inactivated). Management: Vaccine efficacy may be reduced. Complete all age-appropriate vaccinations at least 2 weeks prior to starting fingolimod. If vaccinated during fingolimod therapy, revaccinate 2 to 3 months after fingolimod discontinuation. Consider therapy modification

Immunosuppressants: May diminish the therapeutic effect of Vaccines (Inactivated). Management: Vaccine efficacy may be reduced. Complete all age-appropriate vaccinations at least 2 weeks prior to starting an immunosuppressant. If vaccinated during immunosuppressant therapy, revaccinate at least 3 months after immunosuppressant discontinuation. Exceptions: Cytarabine (Liposomal). Consider therapy modification

Venetoclax: May diminish the therapeutic effect of Vaccines (Inactivated). Monitor therapy