Japanese Encephalitis Vaccination
Japanese encephalitis is a viral illness found throughout most parts of South and South East Asia, where it is the leading cause of viral encephalitis (inflammation of the brain) in children.
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.
Approximately 1 in 250 people became unwell after infection. Children and older adults are at higher risk of developing symptoms.
Symptoms include high fever, convulsions, headache and neck stiffness.
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.
Japanese Encephalitis Vaccine
There is currently only one licensed vaccine against Japanese encephalitis in the UK. It is an inactivated vaccine and cannot cause the disease n the vaccinated individual and nor is the vaccinated individual infectious to others.
The vaccine can be given to individuals aged 2 months and above who are travelling to or going to live in risk areas for Japanese Encephalitis.
|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||Consider booster after 2 years||Unknown|
|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||Consider Booster after 2 years||Unknown|
|Adults over 18 years||Ixiaro||0.5ml||Intramuscular injection to the deltoid muscle||2 doses||2nd dose administered 28 days after 1st dose||Single booster dose 24 months after finishing course. (at 12 months if at continuous risk)||If at risk again vaccinate after ten years.
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.
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
- Yellow fever
- Chicken Pox
- All childhood vaccines
Frequently Asked Questions
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:
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.