Japanese encephalitis virus (JEV) vaccines

Japanese encephalitis virus (JEV) is a vaccine-preventable disease. Read the ATAGI and CDNA information on JEV vaccines to learn about the vaccines available and who they are recommended for.

Japanese encephalitis virus (JEV) is a vaccine-preventable disease. JEV vaccines are recommended for people at risk of exposure to the virus, as advised by your local public health authority.

There are 2 JEV vaccines are registered for use in Australia:

  1. Imojev
  2. JEspect.

These vaccines have been used extensively over many years in Australian Defence Force personnel, residents of the Torres Strait Islands and travellers to southeast Asia.

Both vaccines, as well as other JEV vaccines produced by similar technologies are used extensively in childhood, and some adult, vaccination programs in countries with ongoing transmission of JEV. 

Imojev vaccine

Imojev is a live attenuated vaccine. This means it contains a weakened version of the live JE virus.

It is given as a single dose and recommended for use in people aged 9 months and over.

Imojev is not suitable for:

  • people who have a weakened immune system (immunocompromised)
  • pregnant people
  • infants aged less than 9 months.

A broad use of Imojev is appropriate; it has the benefit of requiring only a single dose and is available where there are constraints on supply of JEspect – the only other vaccine suitable for those who cannot receive Imojev.

Imojev is manufactured by Sanofi.

JEspect vaccine

JEspect is an inactivated vaccine.

JEspect is given as 2 doses, either 28 days apart, or 7 days apart in adults if they are at risk of immediate exposure to the virus. It is recommended for use in people aged 2 months and over. People who have a weakened immune system (immunocompromised) or pregnant people can receive this vaccine.

JEspect is distributed by Seqirus.

Booster doses

A booster dose of either Imojev or JEspect is recommended for people who are at risk of JEV infection (as advised by your local public health authority) and more than one year has passed since their primary JEV vaccine course in childhood, or as an adult.

This includes people who cannot identify the JEV vaccine brand that they received, or those who have received the JEV vaccine previously used in Australia (JEvax), or JEV vaccines that are registered overseas that are used for JEV vaccination programs in endemic countries.

Booster doses are not needed for people who have evidence that they received a dose of Imojev when they were aged 18 years or over.

Getting a Japanese encephalitis vaccine

Communicable Diseases Network Australia (CDNA) jurisdictional representative group has prioritised the following groups for priority vaccination, utilising existing supply on hand in Australia: 

  • people who work at, reside at, or have a planned non-deferable visit to a:
    • piggery, including but not limited to farm workers and their families (including children aged 2 months and older) living at the piggery, transport workers, veterinarians and others involved in the care of pigs
    • pork abattoir or pork rendering plant.
  • personnel who work directly with mosquitoes through their surveillance (field or laboratory based) or control and management, and indirectly through management of vertebrate mosquito-borne disease surveillance systems (e.g. sentinel animals) such as:
    • environmental health officers and workers (urban and remote)
    • entomologists
  • all diagnostic and research laboratory workers who may be exposed to the virus, such as persons working with JEV cultures or mosquitoes with the potential to transmit JEV; as per the Australian Immunisation Handbook.

Contact your local public health authority to find out if you should have a JEV vaccine.

Tell your vaccine provider if you:

  • have had an allergic reaction after a previous dose of a JEV vaccine, or have had an allergic reaction to any component in the vaccine, including protamine sulphate (for the JEspect vaccine)
  • have previously received the JEV vaccine – you may need a booster dose. Your vaccine provider can also record your previous doses of JEV vaccine on the Australian Immunisation Register, even if you were vaccinated overseas
  • are pregnant – pregnant people should not receive Imojev, but they can have JEspect
  • have a weakened immune system – immunocompromised people should not receive Imojev, but they can have JEspect
  • have an infant between 2 months and 8 months of age – the infant should not receive Imojev, but can have JEspect.

People with minor illnesses, such as a cold, can be vaccinated. People who are moderately or severely ill should usually wait until they recover before getting JEV vaccine. Your health care provider can give you more information.

If you have concerns about the nature of the medications you are on, or are uncertain about your degree of immunosuppression, you should not be vaccinated with Imojev, and should seek advice about using the alternative vaccine JEspect.

Vaccine safety

Common side effects of JEV vaccines are:

  • pain
  • tenderness
  • redness
  • swelling where the vaccine was given.

Fever may occur, more often in children. Headache or muscle aches can also occur, mainly in adults. These side effects usually go away within a few days.

Severe reactions to JEV vaccine are very rare. As with any medicine, there is a very small chance of a vaccine causing a severe allergic reaction.

If you are pregnant or breastfeeding

If you are pregnant and are at increased risk of exposure to JEV you should get vaccinated with the JEspect vaccine. JEV infections during the first and second trimesters have been associated with miscarriage. 

No adverse outcomes of pregnancy have been attributed to vaccination with JEspect.

If you are breastfeeding and are at increased risk of exposure to JEV, JEspect is recommended in preference to Imojev. Imojev is not contraindicated in breastfeeding.

Protection after vaccination

More than 95% of people develop a protective immune response to the virus by about 28 days after completing the primary vaccination schedule.

Vaccinated people should still use all precautions to avoid mosquito bites:

You can protect yourself from being bitten by mosquitos by:

  • applying and regularly reapplying an effective insect repellent on exposed skin
  • wearing long, loose fitting clothing when outside
  • ensuring accommodation, including tents, are properly fitted with mosquito nettings or screens
  • using insecticide sprays, vapour dispensing units (indoors) and mosquito coils (outdoors) to clear rooms and repel mosquitoes from an area
  • covering all windows, doors, vents and other entrances with insect screens
  • removing any water-holding containers where mosquitoes may breed.

The best mosquito repellents contain diethyltoluamide (DEET), picaridin, or oil of lemon eucalyptus.

More information

Contact your local public health authority to find out if you should have a JEV vaccine.

Find out more about JEV and the current health alert.

CDNA advice regarding vaccination against Japanese encephalitis virus

Advice regarding vaccination against Japanese encephalitis virus from the Communicable Diseases Network Australia (CDNA) Japanese encephalitis Sub-Group.

Last updated: 
24 March 2022

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