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Vaccine Pregnancy: As a precautionary measure, avoid use during pregnancy (limited data). Avoid during breast-feeding in the absence of data (systemic exposure negligible).

Japanese encephalitis vaccine

Brand names: Ixiaro, JEspect

Japanese encephalitis vaccine is an inactivated vaccine used to provide active immunisation against Japanese encephalitis virus for travellers to, and residents of, endemic areas of Asia.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 0.5 ml per intramuscular dose; primary immunisation is two 0.5 ml doses (IXIARO), for adults 18 to 65 years and elderly over 65 years
Route: Intramuscular (deltoid muscle; anterolateral thigh in infants). Never intravascular. Subcutaneous only in patients with thrombocytopenia or bleeding disorders (may give a suboptimal response)
Frequency: Conventional schedule: dose 1 on Day 0, dose 2 on Day 28. Rapid schedule (adults 18 to 65 years only): dose 1 on Day 0, dose 2 on Day 7
Complete primary immunisation at least 1 week before potential exposure to Japanese encephalitis virus. Booster (third dose) within the second year (12-24 months) after primary immunisation; persons at continuous risk (laboratory staff, residents of endemic areas) should receive the booster at month 12; a second booster 10 years after the first booster. Elderly over 65 years: same two-dose 0.5 ml primary schedule (Day 0, Day 28); protection duration uncertain so consider a booster before further exposure. Paediatric: 3 to less than 18 years — two 0.5 ml doses (Day 0, Day 28), single 0.5 ml booster; 2 months to less than 3 years — two 0.25 ml doses (Day 0, Day 28), single 0.25 ml booster from 14 months (see SPC section 6.6 for preparing a 0.25 ml dose). Not established below 2 months of age.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substance, any excipient, or the residues protamine sulphate, formaldehyde, bovine serum albumin, host cell DNA, sodium metabisulphite or host cell protein
  • Do not give the second dose to anyone who showed hypersensitivity after the first dose
  • Postpone administration in acute severe febrile conditions

Side effects

  • Injection site pain (33%)
  • Injection site tenderness (33%)
  • Headache (20%)
  • Myalgia (13%)
  • Fatigue (12.9%)

Interactions

  • May be given concomitantly with inactivated hepatitis A vaccine and inactivated rabies vaccine without interference with immune responses
  • Immunosuppressive therapy or immunodeficiency may result in an inadequate immune response
  • When co-administered with other injectable vaccines, use separate syringes at opposite injection sites

Clinical monograph

How it works

It contains inactivated Japanese encephalitis virus antigen that stimulates production of protective neutralising antibodies.

Prescribing in practice

  • It is contraindicated in those with a previous severe hypersensitivity reaction to the vaccine or its components.
  • A primary course of two doses is given, ideally completed before travel, with a booster for those at continued risk.
  • Risk assessment should weigh the destination, season, duration and nature of travel against the small vaccine risks.

Monitoring

No routine monitoring is required; observe for immediate hypersensitivity following administration.

Counselling the patient

  • Injection-site soreness, headache and muscle aches are common and usually mild.
  • Complete the full course before travelling to be properly protected.
  • Continue mosquito-bite avoidance measures, as no vaccine is fully protective.

Evidence & guidelines

Travel immunisation recommendations follow the Green Book and UKHSA/NaTHNaC guidance based on destination-specific risk.

Reference: UK Green Book; NaTHNaC; Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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