Japanese Encephalitis
A mosquito-borne virus affecting the brain, found in rural parts of Asia. Risk is highest during rice-paddy season in rural areas.
What it is
Japanese encephalitis is a virus that can cause serious swelling of the brain. Most infections are mild or symptomless, but the rare severe cases can be life-changing.
How it spreads
Mosquitoes pick it up from pigs and water birds in rural farming areas, especially around rice paddies, and pass it to humans. It is found across much of Asia and parts of the western Pacific.
Dosing & timing
- Primary series
- Two shots in your arm, 28 days apart. Adults aged 18 to 65 can use a faster schedule with doses 7 days apart.
- Boosters
- If you remain at risk, a booster after about a year keeps protection going for several years.
- Before you travel
- Finish the second dose at least a week before you leave.
Who should consider it
CDC recommends the vaccine if you are moving to a country where the virus circulates, planning a long stay (a month or more) in rural Asia, or travelling often to those areas. Consider it for shorter trips too if you will spend significant time outdoors in rural areas during transmission season.
Countries where CDC recommends this
Click any country for its full vaccine list.
Recommended for some travellers
Side effects and safety
Common (most resolve in a day or two)
- Soreness or redness where the shot was given
- Headache
- Muscle aches
Serious but rare
- Severe allergic reaction (very rare)
Who should not get it
Skip it if you have had a severe allergic reaction to a previous dose or any ingredient.
Common questions
Do I need this vaccine for a city break in Tokyo or Bangkok?
Probably not. The risk is mainly in rural farming areas during the wet season. Short urban trips usually do not need it.
Is the accelerated schedule as good as the standard one?
Yes. For adults aged 18 to 65, the 7-day schedule gives strong protection and is useful when time is tight.
How long does protection last?
Several years after a booster. If you keep travelling to risk areas, your doctor will check whether you need another.
Plan ahead: Talk to a travel health doctor 4 to 6 weeks before departure — this vaccine needs at least 8 days even on the fast schedule.
Source: CDC — Japanese Encephalitis.
Disclaimer:This information is for general guidance only, based on CDC Travelers' Health. It does not replace advice from a qualified travel health professional. Consult a doctor 4–6 weeks before your trip.