Japanese Encephalitis Vaccination

Japanese encephalitis is a viral illness found throughout most parts of South and South East Asia.

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Japanese encephalitis is the leading cause of viral encephalitis (inflammation of the brain) in children.

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The virus is transmitted by the bite of a mosquito, which feeds from dusk until dawn. Pigs and water birds act as sources of the virus. Thus, the infection is mainly found in rural and semi-rural areas. Transmission can vary by season in individual countries, with highest risk during rainy season. However, other countries have year round transmission.

What are the symptoms of Japanese encephalitis?

Approximately 1 in 250 people became unwell after infection. Children and older adults are at higher risk of developing symptoms.

Japanese encephalitis often starts with flu-like symptoms such as fever, headache, and vomiting. Severe cases can progress to neurological symptoms like seizures, paralysis, and confusion. It’s important to seek medical attention immediately if you suspect you have contracted the virus.

Up to 30% of cases are fatal and 30-50% of individuals who develop encephalitis have permanent neurological disability.


There is no specific treatment for Japanese Encephalitis, only supportive care.


The infection can be prevented by vaccination and mosquito bite prevention measures, such as effective insect repellent and mosquito nets.

There is currently only one licensed vaccine against Japanese encephalitis in the UK. It is an inactivated vaccine and cannot cause the disease in the vaccinated individual and nor is the vaccinated individual infectious to others.

Can children have the Japanese encephalitis vaccine?

Yes, children can receive the Japanese encephalitis vaccine. It is generally recommended for children aged 9 months and older who are travelling to or living in areas with a high risk of Japanese Encephalitis. The dosage and schedule might differ for children, so it’s essential to consult with a healthcare provider.

Who is not able to have the Japanese encephalitis vaccine?

Individuals with severe allergies to any component of the vaccine, particularly those who have had a previous allergic reaction to the vaccine, should not receive it. 

People with weakened immune systems or certain health conditions may need to consult with a doctor.

Age range Vaccine Brand Dose Method of Administration Number of doses primary course Interval between doses primary course First Booster dose requirements Second Booster dose requirements
2 months-3 years of age Ixiaro 0.25ml Intramuscular injection to the thigh or deltoid muscle. 2 doses 2nd dose administered 28 days after 1st dose If at ongoing risk for infection (such as travelling to live in endemic country)-First Booster at 12 months

All other Travellers-First Booster at 12-24 months
Children over 3 years up until 18 years Ixiaro 0.5ml Intramuscular injection to the deltoid muscle 2 doses 2nd dose administered 28 days after 1st dose If at ongoing risk for infection (such as travelling to live in endemic country)-First Booster at 12 months

All other Travellers-First Booster at 12-24 months
Adults 18 years-65 years Ixiaro 0.5ml Intramuscular injection to the deltoid muscle 2 doses Standard Schedule=2 doses given at day 0 and day 28

Rapid Schedule-2 doses at day 0 and day 7
If at ongoing risk for infection (such as travelling to live in endemic country)-First Booster at 12 months

All other Travellers-First Booster at 12-24 months
Second Booster at 10 years if at risk.

The rapid schedule can be used if there is insufficient time to complete the standard schedule.

Adults between 18-65 years-rapid course of 2 doses Ixiaro given at day 0 and second dose 7 days later. This schedule provides the equivalent protection 7 days after the second dose as the standard schedule.

Additionally, the DOH guidance advises that clinical staff can adopt this ACCELERATED schedule “off license” in children aged 12-17 yrs also, if there is insufficient time before departing for their trip.


The vaccine cannot be given to:

  • Infants under 2 months of age
  • Individuals with a history of severe allergic reaction to previous dose of the vaccine or any  of it’s components.
  • Acute illness with high fever (greater than 38.5 degrees Celsius)


There is insufficient data of the effects of the vaccine during pregnancy and therefore, it should not be administered to pregnant women.

Breast Feeding

Vaccination during breast feeding should be avoided due to lack of safety data.

Common Side Effects

Local injection site reactions including redness, swelling and pain.

Other side effects include fever, “flu-like” illness, muscle aches.

Interactions with Other Vaccines

The Japanese Encephalitis vaccine can be given at the same time as other vaccines including:

  • Hepatitis A
  • Hepatitis B
  • Rabies
  • Yellow fever
  • Typhoid
  • MMR
  • Chicken Pox
  • All childhood vaccines

Japanese encephalitis vaccine is recommended for travellers to certain areas where the disease is prevalent, especially when travelling to areas where you spend a lot of time outdoors or stay in rural areas.

It is particularly advised for those traveling to parts of Asia and the Western Pacific. The risk of Japanese encephalitis for most travellers is generally low but can vary based on the destination, duration of travel, season, and activities. Consulting a healthcare provider or a travel medicine specialist can help determine if you need the vaccine based on your travel itinerary.

The duration of protection provided by the Japanese encephalitis vaccine is typically long-lasting. After completing the primary vaccination series, which is 2 doses the protection can last at least several years. However, the exact duration can vary depending on the specific vaccine used. For ongoing risk or long-term exposure, a booster dose may be recommended, usually after 1 to 2 years for the inactivated vaccines.

Booster doses for the Japanese encephalitis vaccine are typically recommended for those who continue to be at risk of exposure. If the primary series was completed more than 1 to 2 years ago and there is ongoing risk, a booster dose is advised. 

The schedule may vary depending on the specific vaccine and individual risk factors, so it’s important to consult with a healthcare provider for personalised advice.

Japanese encephalitis is primarily found in rural and agricultural areas in Asia and the Western Pacific. Countries with a higher risk include India, China, Nepal, Myanmar, Thailand, Vietnam, Laos, Cambodia, Malaysia, Indonesia, the Philippines, and parts of Korea and Japan. 

The risk can vary within a country and depending on the season, with the highest risk often during the monsoon season.

The cost of each Japanese encephalitis vaccination dose is £119. Initially, there is an additional base fee of £20 which covers time spent with one of our specially trained healthcare professionals who will carry out a risk assessment.

However, for the second dose, only the vaccine cost of £119 applies, as the base fee is not charged again.

Common side effects of the Japanese encephalitis vaccine include pain and redness at the injection site, headache, and muscle aches. These are usually mild and resolve within a few days. Rare side effects can include allergic reactions, such as hives or difficulty breathing, which require immediate medical attention. Serious neurological side effects are extremely rare.

The Japanese encephalitis vaccine is not typically available on the NHS for general use. It may be available for specific groups at risk or for travel purposes, but this depends on individual circumstances. Travellers usually need to visit a travel clinic and pay for the vaccine privately.

1) How long does take for the vaccine to become effective?

The vaccine is effective 7 days after the second dose has been received.

2) What does the vaccine contain?

The vaccine contains the following ingredients:

  • Phosphate buffered saline consisting of:
  • Sodium chloride
  • Potassium dihydrogen phosphate
  • Disodium hydrogen phosphate
  • Water for injections
  • aluminium hydroxide

The vaccine does not contain the following:

  • Latex
  • Gelatin
  • Thiomersal
  • Egg

3) If I had a different brand of Japanese encephalitis, do I need to restart the course?

Previously, Green Cross vaccine was available in the UK, which consisted of a three dose course. The Department of Health advises that adults who have had a previous course of any Japanese encephalitis vaccine can receive a single dose of IXIARO® as a booster.

4) If I travel regularly to risk areas , would I need further booster?

The advice on long term protection and further boosters in adults is not known currently. The vaccine manufacturers have advised the following in their product description:

“Long-term seroprotection data following a first booster dose administered 12 – 24 months after primary immunization suggest that a second booster should be given 10 years after the first booster dose, prior to potential exposure to JEV”. (SPC Ixiaro)

However, we would need to wait for the advice from the UK’s Joint Committee on Vaccinations and Immunisations for confirmation of this.

5) What about boosters in children?

The Department of Health advises that if children under 18 years are at continued risk of infection, then a booster dose can be considered.

6) Can the vaccine be given to infants under 2 years of age?

The vaccine cannot be given infants under 2 months of age, as there is no data on safety or effectiveness  in this age group.

7) How effective is one dose of the Japanese Encephalitis vaccine?

Clinical studies show that one dose of the Japanese encephalitis vaccine provides around 21% protection 10 days after receiving the first dose and around  40% protection 28 days after the first dose. 

Therefore, if there is not enough time to complete the 2 dose course, additional insect bite prevention measures are vital in protecting against contracting the infection.

8) Can the second dose be given later than 28 days?

The second dose of Japanese encephalitis vaccine can be given up to 11 months after the 1st dose and still provide an effective immune response. 

9) How does Japanese encephalitis interact with other vaccines?

The Japanese encephalitis vaccine can be given at the same time as most other vaccines, including yellow fever and typhoid. 

If not administered simultaneously, it’s generally advised to wait at least a few weeks between different live vaccines. It’s important to discuss your vaccination history with a healthcare provider to ensure proper scheduling.

Written by Travel Health and Vaccination Lead Derek Evans

Edited on 06-02-2024
Next edit on 26-11-2024

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Our pre-travel consultations are with experienced travel health specialists and pharmacists who will assess the impact of any pre-existing medical conditions along with your vaccine requirements. They will discuss in detail countries at risk, precautions you can take to avoid exposure and how to travel safely. We also highly recommend visiting the government websites which has the latest travel news and advice for every destination.

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