Vaccine Info

Ixiaro Japanese Encephalitis Vaccine

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Last reviewed
April 6, 2021

Ixiaro Vaccine Description

Ixiaro is an inactivated, adsorbed Vero cell culture-derived vaccine targeted against the Japanese encephalitis virus (JEV). It is prepared by propagating JEV strain SA14-14-2 in Vero cells. Multiple viral harvests are pooled, clarified, and concentrated. The virus suspension is treated with protamine sulfate to remove contaminating DNA and proteins.

The resulting partially purified virus is processed through a sucrose density gradient centrifugation step and fractionated. Each fraction is analyzed for the presence of the virus, and fractions with the highest virus activity are pooled to give a purified virus suspension.

The purified virus is then inactivated by treatment with formaldehyde. The preparation is adjusted to a specified protein concentration and formulated by the addition of aluminum hydroxide.

France based Valneva SE's IXIARO is the only vaccine approved by the U.S. FDA against JV. The IXIARO vaccine was developed through a cooperative research and development agreement with the Walter Reed Army Institute of Research. Valneva markets and distributes IXIARO® directly to the U.S. military and U.S. private market.

The Ixiaro vaccine was approved on March 30, 2009. Currently, Ixiaro is licensed in Australia, New Zealand, Europe, Canada, Switzerland, Hong Kong, Singapore, and Israel. Valneva IXIARO helps prevent the Japanese Encephalitis virus which is a leading cause of vaccine-preventable encephalitis. 

Visit, a website for travel health professionals and their patients, focusing on the risk and prevention of Japanese encephalitis for travelers to Asia.

Valneva is a specialty vaccine company focused on the prevention against diseases with major unmet needs. For more information, visit

Ixiaro Vaccine Indication

The JE virus is the leading cause of vaccine-preventable encephalitis in Asia and the western Pacific. For most travelers to Asia, the risk for JE is very low but varies based on the destination, length of travel, season, and activities. Ixiaro is indicated for active immunization for the prevention of disease caused by Japanese encephalitis virus (JEV) and is approved for use in individuals 2 months of age and older.

Vaccination with IXIARO may not protect all individuals. Immunocompromised individuals may have a diminished immune response to IXIARO.  Syncope can occur in association with the administration of injectable vaccines, including IXIARO. Procedures should be in place to prevent injury from falling and manage syncopal reactions.

Ixiaro Vaccine Dosage

Ixiaro is administered as an intramuscular injection and is approved for use in individuals 2 months of age and older. In 2019, the U.S. CDC's ACIP committee strengthened its language on booster doses to say they should be given at least 1 year after the primary series if the person is experiencing ongoing exposure or re-exposure to the JE virus.   

Primary Series:

Children 2 months to <3 years of age: Primary immunization with IXIARO consists of two (2) 0.25 mL doses, administered 28 days apart.

Individuals 3 years of age and older: Primary immunization with IXIARO consists of two (2) 0.5 mL doses, administered 28 days apart.

Complete the primary immunization series at least 1 week prior to potential exposure to JEV.

Booster Dose:

Individuals 17 years of age and older: If the primary series of two doses was completed more than 1 year previously, a booster dose may be given if ongoing exposure or re-exposure to JEV is expected.

Infants, children, and adolescents 2 months to <17 years of age: The safety and immunogenicity of a booster dose have not been evaluated.

Ixiaro Vaccine News

September 9, 2020 - Valneva SE announced the signing of a new contract, lasting up to 3-years, with the U.S. Department of Defense (DoD) for the supply of its Japanese encephalitis vaccine, IXIARO®. This new contract has one base year, plus two option years, with a base-year value of $61 million. Deliveries for the base year will commence in the fourth quarter of 2020. The DoD has the option to purchase a total of $76 million – $105 million worth of IXIARO® across the 2 option years.

March 8, 2020 – Valneva SE announced that the Food and Drug Administration (FDA) has approved the extension of the shelf life of its Japanese encephalitis vaccine IXIARO from 24 months to 36 months.

January 14, 2020 – The U.S. Department of Defense (DoD) has exercised an option to purchase 80,000 additional doses of its Japanese encephalitis (JE) vaccine IXIARO®.

July 19, 2019 - Japanese Encephalitis Vaccine: Recommendations of the Advisory Committee on Immunization Practices.

June 5, 2019: The European Medicines Agency (EMA) has approved the extension of the shelf life of the Japanese encephalitis vaccine IXIARO from 24 months to 36 months.

March 1, 2019 – According to 2 unanimous votes by the Advisory Committee on Immunization Practices (ACIP) committee at its February 27, 2019 meeting, Japanese Encephalitis (JE) virus vaccination recommendations have been expanded. 

Ixiaro Vaccine Clinical Trials

Ixiaro Japanese Encephalitis vaccine has been involved in over 60 clinical trials.  

Clinical Trial NCT00604708: Immunogenicity Phase 3 Study of the Japanese Encephalitis Vaccine IC51

Clinical Trial NCT01386827: Phase 3 study Ixiaro as Booster After Mouse-brain Derived Vaccines for Japanese Encephalitis

Japanese Encephalitis Virus Overview

JE is a mosquito-borne flavivirus, is the most common vaccine-preventable cause of encephalitis in Asia. JE occurs throughout most of Asia and parts of the western Pacific (3,4). Approximately 20%–30% of patients die, and 30%–50% of survivors have neurologic, cognitive, or behavioral sequelae. In countries where the disease is endemic, JE primarily affects children. Although rare, travel-associated JE can occur among persons of any age (8–10). For most travelers to Asia, the risk for JE is very low but varies based on travel duration, season, location, activities, and accommodations.

JE virus is maintained in an enzootic cycle between mosquitoes and amplifying vertebrate hosts, primarily pigs and wading birds (12,13). JE virus is transmitted to humans by infected mosquitoes (1). JE virus transmission occurs primarily in rural agricultural areas. In most temperate areas of Asia, JE virus transmission is seasonal, and large outbreaks can occur. In the subtropics and tropics, transmission can occur year-round, often intensifying during the rainy season.

Japanese Encephalitis news is published by Precision Vaccinations. 


Clinical Trials

No clinical trials found