IXIARO® suspension for injection

Japanese encephalitis vaccine (inactivated, adsorbed). Prescription only medicine.

OVERVIEWCLINICAL DATADOSING & ADMINISTRATION

IXIARO® EFFICACY

IXIARO® offers protection from infancy to adulthood, with seroconversion rates of ≥96% recorded across all age groups and dosage schedules 28 days following primary immunisation.1,2

Immune response 28 days following primary immunisation®1,2

SRR = seroresponse rate

*The conventional schedule for IXIARO® administration is two doses, 28 days apart.

**The rapid schedule, tested in adults aged 18–65 years, reduced this to two doses seven days apart. Doses of the Rabipur® vaccine were administered to recipients of the rapid schedule on days 0, 3, and 7.

Seroconversion and protective antibodies

  • Seroconversion is the point at which a person’s blood changes from having no detectable antibodies against a pathogen to having detectable antibodies, indicating a recent or ongoing immune response3
  • IXIARO® clinical trials used seroconversion rates in vaccinated participants to measure vaccine effectiveness2,3
  • The World Health Organization (WHO) defines a PRNT50 titre ≥1:10 as indicative of protective immune response4

PRNT50 titre ≥1:10 details

  • The plaque reduction neutralisation test (PRNT), measures virus-neutralising antibodies that correlate with protection5
  • The virus-neutralising antibody titre is expressed as the serum dilution producing a 50% reduction in plaques compared with virus-only controls (PRNT50)6
  • All PRNT50 results are expressed as reciprocal titres, and geometric mean titres (GMTs) were calculated as the geometric mean of PRNT50 values2
  • Clinical efficacy was specified using a cutoff of a neutralising antibody titre of ≥1:102

RAPID SCHEDULE

While the conventional schedule is two doses on 28 days apart, clinical trial data shows that IXIARO® remains effective in adults aged 18–65 years when delivered over a short period of time (two doses seven days apart). A seroconversion rate of 99% was reported in patients following the rapid schedule one week after the second dose.2 This makes IXIARO® an option for travellers with last minute plans to visit a JE endemic area and as a response to outbreaks.

SAFETY AND TOLERABILITY

IXIARO® has a generally well tolerated safety profile for individuals of all ages, supported by more than 16 years of real-life experience.2,7

ADVERSE EVENTS

In children and adults, most adverse events are usually mild and resolve within a few days.2 The frequency of adverse events between older and younger adults is comparable.2

The figure below shows the most common adverse events by age group.2,8

IXIARO® safety profile2,8

BOOSTER DOSE GRANTS LONG-TERM PROTECTION

A booster dose administered approximately 12–24 months after primary immunisation is estimated to offer travellers a further decade of protection.2

LEARN MORE ABOUT IXIARO®

Delve deeper into the product features, clinical findings and dosing recommendations.

IXIARO® suspension for injection

OVERVIEW

Get a useful overview of IXIARO®, including key facts about the vaccine.

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IXIARO® suspension for injection

DOSING & ADMINISTRATION

IXIARO® is administered in two doses for adults and children >2 months.

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References
  1. Tauber E, Kollaritsch H, Korinek M, et al. Safety and immunogenicity of a Vero-cell-derived, inactivated Japanese encephalitis vaccine: a non-inferiority, phase III, randomised controlled trial. Lancet. 2007;370(9602):1847-1853.
  2. IXIARO®. Summary of Product Characteristics. March 2023. Available at: https://www.medicines.org.uk/emc/product/6534. Accessed: August 2026.
  3. National Cancer Institute. Definition of seroconversion. February 2011. Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/seroconversion. Accessed: August 2026.
  4. Hombach J, Solomon T, Kurane I, Jacobson J, Wood D. Report on a WHO consultation on immunological endpoints for evaluation of new Japanese encephalitis vaccines, WHO, Geneva, 2–3 September, 2004. Vaccine. 2005;23(45):5205-5211.
  5. Denani C, Horbach I, Setatino B, et al. Evolution of the PRNT: Merging tradition and innovation to set the gold standard in the era of automation. Human Vaccines & Immunotherapeutics. 2025;21(1):2528368.
  6. Tyagi P, Ganguly M, Manney S, et al. Plaque reduction neutralization test (PRNT50) for the detection of anti-yellow fever antibodies from clinical samples. Vaccine. 2026;73:128151.
  7. Yun SI, Lee YM. Japanese encephalitis: the virus and vaccines. Hum Vaccin Immunother. 2014;10(2):263-279.
  8. Cramer JP, Dubischar K, Eder S, et al. Immunogenicity and safety of the inactivated Japanese encephalitis vaccine IXIARO® in elderly subjects: Open-label, uncontrolled, multi-center, phase 4 study. Vaccine. 2016;34(38):4579-4585.

IXIARO® suspension for injection

UK-IXI-2600001 (v2.0) August 2026