Japanese Encephalitis
日本腦炎疫苗
A travel vaccine for specific itineraries — rural Asia in summer, long stays, outdoor exposure. Not routine for most HK travellers.
Ixiaro
Japanese encephalitis (JE) is a viral brain infection spread by mosquitoes, mainly Culex species that breed in rice paddies and pig farms. It is the leading cause of viral encephalitis across Asia.
Around 1 in 250 infected people develop encephalitis — roughly 30% die and many survivors have lasting neurological damage.
The vaccine is inactivated (Ixiaro is the main product in HK) — no live virus, no risk of vaccine-induced infection.
HK Travel Health Service recommends JE vaccination for travellers who plan to:
- Spend a month or longer in rural areas of endemic countries during transmission season
- Travel for shorter periods but with significant outdoor or rural exposure
- Travel to areas with active JE outbreaks
Routine urban tourism in JE-endemic countries does not usually warrant vaccination. Speak with a Travel Health Service clinic 4-6 weeks before travel.
US CDC recommendation broadly aligned: JE vaccine for travellers spending a month or more in endemic areas, or shorter stays with high outdoor exposure during transmission season.
Adults (Ixiaro): 2 doses, 28 days apart. Accelerated schedule (0, 7 days) is approved for adults 18-65 if time is tight.
Children (Ixiaro): approved from 2 months of age. Same 2-dose schedule, paediatric dose.
Aim to complete the course at least 1 week before travel.
| Brand | Manufacturer | HK Reg No. |
|---|---|---|
| Ixiaro · Inactivated, Vero cell-derived JE vaccine | Valneva |
Sore arm, headache, muscle aches, mild fever, tiredness. Serious reactions are very rare. Modern Ixiaro has a much cleaner safety profile than older mouse-brain-derived JE vaccines.
Myth: I'm going to Asia for a holiday — I need every travel vaccine.
Reality: JE is for specific itineraries — rural, outdoor, long stays, transmission season. A 1-week city trip usually doesn't need it. Talk to a travel health clinic about your specific plan.
- HK Travel Health Service clinics: public service offering travel vaccinations including JE
- Private travel medicine clinics: widely available; book 4-6 weeks before travel
- Some GP clinics stock JE vaccine for established travel patients
- HK Travel Health Service — Japanese Encephalitis · HK Travel Health Service (HK)
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