Vaccine Info

Ixiaro Japanese Encephalitis Vaccine

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Last reviewed
May 8, 2024
Fact checked by
Robert Carlson, MD

IXIARO® JESPECT® Japanese Encephalitis Vaccine Clinical Trials, Dosage, Indication, Side Effects

Valneva SE's IXIARO® JESPECT® 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 partially purified virus is processed and fractionated through a sucrose density gradient centrifugation. 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. IXIARO's final preparation is adjusted to a specified protein concentration and formulated by adding aluminum hydroxide.

The IXIARO JEV was developed through a cooperative research and development agreement with the Walter Reed Army Institute of Research. Valneva SE markets and distributes IXIARO® directly to the U.S. military and private markets. The U.S. Department of Defense (DoD) has relied on IXIARO since 2010 to help protect personnel deployed to JE endemic areas for whom JE vaccination is recommended. Visit, a website for travel health professionals and their patients, focusing on the risk and prevention of Japanese encephalitis for travelers to Asia

On My 7, 2024, Vaneva announced IXIARO®/JESPECT® first quarter of 2024 sales were €16.6 million compared to €17.4 million in the first quarter of 2023. Sales to the U.S. military counterbalanced most of the supply constraints experienced during the period. These constraints have now been resolved. Valneva expects double-digit annual growth for IXIARO® sales for at least the next three years. At the end of September 2023, Valneva signed a new one-year contract with the U.S. Department of Defense for the supply of IXIARO® worth a minimum of $32 million.

France-based Valneva SE (Nasdaq: VALN; Euronext Paris: VLA) is a specialty vaccine company focused on preventing diseases with significant unmet needs. For more information, visit www.valneva.comValneva USA, Inc. is located at 910 Clopper Road, Suite 160S, Gaithersburg, MD 20878, USA.

IXIARO Vaccine Availability 2024

Valneva SE's IXIARO is the only Japanese encephalitis vaccine approved by the U.S. Food and Drug Administration (FDA) against JEV. The FDA approved the Ixiaro vaccine (STN: BL 125280) on March 30, 2009. The STN: BL 125280/251 was issued on October 4, 2018, to include data to support the concomitant use of IXIARO primary immunization series, to 0.5 mL doses administered 28 days apart with U.S. licensed rabies vaccines (RabAvert) administered for pre-exposure prophylaxis. On March 8, 2020Valneva announced that the FDA approved an extension of the shelf life of IXIARO from 24 months to 36 months. Under a new one-year contract announced on September 25, 2023, the U.S. DoD will buy a minimum of $32 million worth of IXIARO® vaccines and can purchase additional doses during twelve months. Vaccine deliveries will commence in 2023.

IXIARO / JESPECT® is licensed for adults in the U.S.Australia, New Zealand, Europe, Canada, Switzerland, Hong Kong, Singapore, Israel, Norway, Liechtenstein, Iceland, Singapore, Japan, the United Kingdom, and the Republic of Korea. In all other licensed territories, IXIARO®/JESPECT® is indicated for use by adults aged 18 years or older.

IXIARO Indication

IXIARO is indicated for active immunization to prevent disease caused by the JEV, the leading cause of vaccine-preventable encephalitis, and is approved for use in individuals two months of age and older. JE is a deadly infectious isease, occurring throughout most of Asia and parts of the western Pacific. JE is fatal in approximately 30% of those who show symptoms, leaving half of the survivors with permanent brain damage. Since 1993, when a JE vaccine became available in the United States, only 13 JE cases among US travelers have been reported to the U.S. CDC (1993–2020). The overall incidence of JE among people from nonendemic countries traveling to Asia is estimated to be <1 case per 1 million travelers. However, expatriates and travelers who stay for prolonged periods in rural areas with active JE virus transmission might be at similar risk as the susceptible pediatric resident population, which is 6–11 cases per 100,000 children per year. Vaccination with IXIARO may not protect all individuals. Immunocompromised individuals may have a diminished immune response to IXIARO.

IXIARO Side Effects

IXIARO contains protamine sulfate, a compound known to cause hypersensitivity reactions in some individuals. Therefore, severe allergic reaction (e.g., anaphylaxis) after a previous dose of IXIARO®, any other Japanese encephalitis vaccine, or any component of IXIARO®, including protamine sulfate ─ a compound known to cause hypersensitivity reactions in some individuals ─ is a contraindication to administration of IXIARO®. Individuals with a history of severe allergic reaction to another Japanese encephalitis vaccine may be referred to an allergist for evaluation if immunization with IXIARO® might be considered. The most common ( > 10%) adverse reactions were fever, irritability, diarrhea, and injection site redness in infants two months to < 1 year of age; fever in children 1 to < 12 years of age; pain and tenderness in adolescents 12 to < 18 years of age; and, headache, myalgia, and injection site pain and tenderness in adults.


IXIARO is administered as an intramuscular injection and is approved for use in individuals two months 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 one 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 one week before potential exposure to JEV.

Booster Dose: Individuals 17 years of age and older: If the primary series of two doses was completed more than one year previously, a booster dose might be given if ongoing exposure or re-exposure to JEV is expected; Infants, children, and adolescents two months to <17 years of age: The safety and immunogenicity of a booster dose have not been evaluated.

Japanese Encephalitis Outbreaks

The World Health Organization (WHO) says JE transmission intensifies during the rainy season, during which vector populations increase. However, there has not yet been evidence of increased JEV transmission following major floods or tsunamis. On April 28, 2022, the WHO reported Australia's JEV outbreak had confirmed 35 cases and three fatalities across four states. In addition, Australia's government declared a JEV outbreak in Queensland a Communicable Disease Incident of National Significance in March 2022. The U.S. Centers for Disease Control and Prevention (CDC) updated an Alert - Level 2, Practice Enhanced Precautions on December 14, 2022, regarding the JE outbreak in parts of eastern and southeastern Australia.

IXIARO Vaccine News

February 15, 2024 - Peter Bühler, Valneva's Chief Financial Officer, commented, "In 2023, Valneva successfully executed key strategic objectives despite a difficult economic environment."

September 25, 2023 - Dipal Patel, Chief Commercial Officer of Valneva SE, commented, "We are excited to continue our long-term relationship with the DoD. The U.S. military has trusted IXIARO® for over ten years to help protect military personnel, their families, civilian government service personnel, and government contractors from this potentially deadly disease."

September 21, 2023 - Valneva SE confirmed it distributes IXIARO® directly to the U.S. DoD.

July 11, 2022 - A non-peer-reviewed study: Safety and immunogenicity following co-administration of Yellow fever vaccine with Tick-borne encephalitis or Japanese encephalitis vaccines concluded: Inactivated TBEV or JEV vaccines can be co-administered with the live attenuated YFV vaccine without an increased risk of adverse events and reduced development of nAbs to the respective viruses.

September 3, 2021 - Valneva SE announced that the U.S. Department of Defense had exercised the first option of the contract signed in September 2020 to purchase a further supply of its Japanese encephalitis vaccine, IXIARO®.

July 19, 2019 - The CDC's Advisory Committee on Immunization Practices (ACIP) Recommendations for Japanese Encephalitis Vaccine were updated.

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

March 1, 2019 – According to unanimous votes by the U.S. CDC's ACIP at its February 27, 2019 meeting, the JEV vaccination recommendations have been expanded. 

Ixiaro Clinical Trials

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

Clinical Trials

No clinical trials found