The Basics
What Causes Japanese Encephalitis?
Japanese Encephalitis is a serious brain infection caused by the Japanese Encephalitis Virus (JEV). It is transmitted to humans through the bite of infected mosquitoes (primarily the Culex species), which often breed in rice paddies and agricultural areas. While most infections are mild, the virus can cause inflammation of the brain (encephalitis), which can lead to permanent neurological damage or death.
Vaccination Overview
The Japanese Encephalitis Vaccine
| Feature | Details |
| Number of Doses | A standard course consists of two doses |
| Timing | The second dose is given 28 days after the first. |
| Accelerated Schedule | For adults (18–65), an accelerated schedule can be given with the second dose at 7 days. |
| The Booster | A booster is recommended 12 to 24 months after the primary course if you remain at risk. |
| How it is given | Administered as an injection into the upper arm. |
| Suitable Age | Suitable for adults and children 2 months of age and older. |
Safety & Side Effects
What to Expect After Vaccination
The vaccine is generally very safe. Side effects are similar to other routine vaccinations and usually resolve quickly:
Local reaction: Pain, tenderness, or redness at the injection site.
General: Headache or muscle aches (myalgia).
Less Common: Fatigue, nausea, or a mild fever.
Recognising Symptoms
Symptoms of the Infection
Most people infected with JEV show no symptoms or only mild, flu-like signs. However, about 1 in 250 cases result in severe disease.
Initial Signs: Sudden onset of high fever, headache, and vomiting.
Neurological Changes: Confusion, disorientation, or a “mask-like” facial expression.
Severe Symptoms: Tremors, seizures (especially in children), and paralysis.
Progression: Rapid progression to inflammation of the brain (encephalitis), which requires immediate hospitalisation.
Additional Precautions
Preventing Mosquito Bites
Because the vaccine is highly effective but the mosquitoes that carry JEV can also carry other diseases, you should always practice bite prevention:
Insect Repellent: Use a high-quality repellent containing DEET, Picaridin, or Lemon Eucalyptus oil.
Cover Up: Wear long-sleeved shirts and long trousers, especially during the evening and night when Culex mosquitoes are most active.
Sleep Safety: Use mosquito nets (ideally treated with insecticide) and stay in rooms with screened windows or air conditioning.
FAQ
Who is at the highest risk for Japanese Encephalitis?
Travelers spending long periods in rural or agricultural areas in Asia, particularly during the rainy season or near rice fields and pig farms.
Can the vaccine be given at the same time as other travel vaccines?
Yes, the Japanese Encephalitis vaccine can typically be administered at the same time as others, such as Hepatitis A or Typhoid, but in a different injection site.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. While we strive to provide accurate health information, it is not a substitute for the professional judgment of a healthcare provider. Always seek the advice of your physician or other qualified health professional with any questions you may have regarding a medical condition or vaccination schedule. Never disregard professional medical advice or delay seeking it because of something you have read on this website.