What is the recommended Japanese encephalitis (JE) vaccination schedule for adults and children?

Japanese Encephalitis Vaccination Schedule

The Japanese encephalitis vaccine (JE-VC) requires a 2-dose primary series with age-specific dosing: children 2-35 months receive 0.25 mL on days 0 and 28, children 3-17 years receive 0.5 mL on days 0 and 28, adults 18-65 years receive 0.5 mL on days 0 and 7-28 (accelerated option), and adults >65 years receive 0.5 mL on days 0 and 28, all administered intramuscularly. 1

Age-Specific Primary Vaccination Schedules

Infants and Young Children (2-35 months)

• Dose: 0.25 mL per injection 1
• Schedule: Days 0 and 28 1
• Route: Intramuscular (IM) in anterolateral thigh 2
• Preparation note: Expel and discard half the volume from the 0.5 mL prefilled syringe to achieve the 0.25 mL dose 1, 2

Children and Adolescents (3-17 years)

• Dose: 0.5 mL per injection 1
• Schedule: Days 0 and 28 1
• Route: Intramuscular in deltoid muscle 2

Adults (18-65 years)

• Dose: 0.5 mL per injection 1
• Schedule: Days 0 and 7-28 (flexible interval) 1
• Route: Intramuscular in deltoid muscle 2
• Key advantage: This is the only age group approved for an accelerated schedule (7-day interval), allowing for last-minute travel preparation 1

Older Adults (>65 years)

• Dose: 0.5 mL per injection 1
• Schedule: Days 0 and 28 (no accelerated option) 1
• Route: Intramuscular in deltoid muscle 2

Critical Timing Requirement

Complete the 2-dose series at least 1 week before potential JE virus exposure for all age groups. 1, 2 This minimum interval allows adequate immune response development, though protection is not optimal at this early timepoint. 3

Booster Dose Recommendations

• Timing: A booster dose is recommended 12-24 months after the primary 2-dose series for those with continued risk 1
• Dose: 0.25 mL for children <3 years; 0.5 mL for those ≥3 years 1
• Long-term protection: Clinical data demonstrate seroprotection rates of 96% at 6 years post-booster, with predicted protection lasting approximately 14 years 4
• Subsequent boosters: No current U.S. recommendations exist for additional booster doses beyond the first, though data suggest boosters every 10 years may be appropriate for ongoing risk 4

Administration Technique

Injection Site and Needle Specifications

• Infants (2-35 months): Anterolateral thigh, 7/8-1 inch needle, 22-25 gauge 2
• Children ≥3 years and adults: Deltoid muscle, 1-1½ inch needle, 22-25 gauge 2
• Angle: 90 degrees for all intramuscular injections 2

Vaccine Preparation

• Shake the syringe well before administration to obtain a white, opaque, homogeneous suspension 1, 2
• The vaccine may appear as clear liquid with white precipitate during storage—this is normal 1

Concomitant Vaccine Administration

JE-VC can be safely administered simultaneously with hepatitis A vaccine and rabies vaccine without interference in immune response. 1, 2 When giving multiple vaccines:

• Use separate syringes 1, 2
• Administer at different anatomical sites, ideally >1 inch apart 1, 2

Important Contraindications and Precautions

Absolute Contraindication

• Severe allergic reaction (anaphylaxis) to previous JE-VC dose, any JE vaccine component, or protamine sulfate 1

Precaution

• Pregnancy: Vaccination during pregnancy is a precaution; assess risk-benefit on individual basis 1

Storage Requirements

• Store at 35°F-46°F (2°C-8°C) 1
• Do not freeze 1
• Protect from light 1

Common Pitfalls to Avoid

• Do not administer subcutaneously: JE-VC must be given intramuscularly, unlike the discontinued mouse brain-derived vaccine (JE-MB) which was subcutaneous 2
• Do not use accelerated schedule in those >65 years: Only adults 18-65 years are approved for the 7-day interval 1
• Do not assume immediate protection: Even with the accelerated schedule, allow at least 1 week after series completion before exposure 1
• Do not forget to shake: Failure to shake the syringe results in improper suspension and potentially inadequate dosing 1, 2