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
What is it?
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 Department of Health recommendation
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.
International reference (US CDC)
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.
Schedule
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.
HK-registered products
| Brand | Manufacturer | HK Reg No. |
|---|---|---|
| Ixiaro · Inactivated, Vero cell-derived JE vaccine | Valneva |
Side effects
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.
Common myths
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.
Where to get it
- 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
Sources
- HK Travel Health Service — Japanese Encephalitis · HK Travel Health Service (HK)
Related vaccines
Related questions
The recommender
Answer six short questions to see which vaccines are worth discussing with your GP, and why.
Based on your age, health, and travel plans, using HK Department of Health and CDC guidance. A ranked list of vaccines, with the reason each one applies to you.
Rule-based
The recommendations follow HK Department of Health and US CDC guidance, and you can see how each one was reached.
Private
Your answers stay on your own device. We never receive or store them.
Explained
Every recommendation comes with the reason it applies to you.