Japanese encephalitis – frequently asked questions (FAQs)

NCIRS fact sheets, FAQs and other resources

Key points

Japanese encephalitis (JE) is a rare but serious illness caused by the JE virus. It is spread through the bites of infected mosquitoes.
Most people who are infected with the JE virus are asymptomatic, but in severe cases the infection can lead to encephalitis (swelling of the brain), which can cause permanent disability or be fatal.
JE virus occurs in parts of Asia and the Western Pacific region. Travellers to certain risk areas outside Australia are recommended to get vaccinated before travel.
Since 2021, JE cases have been reported in Australia. Some states and territories now have JE vaccination programs for people living or working in – and, in some cases, travelling to – risk regions.
In Australia, two JE vaccines, JEspect and Imojev, are available for people at risk of JE infection.
JEspect is an inactivated vaccine given to people aged 2 months and over via a two-dose schedule. A booster dose is recommended after 1–2 years if there is ongoing risk of exposure to the JE virus.
Imojev is a live vaccine administered as a single dose for people aged 9 months and over. No booster dose is needed if the individual was vaccinated at 18 years of age or over. Because Imojev is a live vaccine, it cannot be given to pregnant women or immunocompromised people.

Last updated: 20 June 2025

FAQs

What is Japanese encephalitis (JE)?

Japanese encephalitis (JE) is a rare but serious brain infection caused by the JE virus. It can lead to neurological complications and death.

How is JE virus spread?

The virus can spread to humans by certain types of mosquito.

Mosquitos can become infected by biting infected animals (such as pigs or waterbirds) and then pass on the infection by biting a human.

Humans cannot transmit the JE virus to other people or mosquitos.

It is not possible to get the virus by eating the meat of an infected animal.

What are the symptoms of JE?

Most people who get JE virus will show no symptoms. Some people (less than 10%) who get infected may experience symptoms such as fever, headache and vomiting.

A small proportion of people with JE infection (less than 1 in 200 of those who get infected) develop encephalitis, which can cause symptoms such as neck stiffness, confusion, seizures and coma.

Among those who develop serious illness from JE infection, there is a risk of permanent neurological damage or death.

What is the difference between JE and Murray Valley encephalitis?

The JE and Murray Valley encephalitis (MVE) viruses are closely related but different viruses. They can both be spread by the same species of mosquitoes.

There are only vaccines for the JE virus. Currently, there is no sufficient evidence that JE vaccines protect people against the MVE virus.

More information about MVE is available from the government-funded service healthdirect as well as state and territory health department websites.

What are the best ways to prevent JE?

For individuals who are living in (or travelling to) a risk region, the best ways to prevent JE are to:

avoid being bitten by mosquitoes
get vaccinated against the JE virus.

More information about mosquito prevention and JE vaccination can be found in:

the Australian Government Department of Health, Disability and Ageing Japanese encephalitis resource collection
the Australian Immunisation Handbook Japanese encephalitis chapter.

Who is at risk of catching JE?

Anyone who is in a region of the world where JE virus has been detected, and who could be bitten by mosquitoes, may be at risk of getting the JE virus.

Who is recommended to receive a JE vaccine?

JE vaccination is recommended for the following groups who are at risk of catching the JE virus:

people who live in (or are travelling to) a risk region* of Australia and who may be bitten by mosquitoes, including those who:
- regularly spend time outdoors
- are experiencing homelessness or living in conditions without mosquito protection
- are taking part in outdoor activities such as camping, fishing or hunting
- live near a piggery, pig abattoir or pig transport business
- are taking part in flood recovery or other natural disaster response activities
- work in a high-risk occupation that involves exposure to pigs or mosquitoes (e.g. veterinarians, piggery workers, environmental health workers).
laboratory workers who may be exposed to JE virus
travellers (especially long-term travellers) to certain regions outside of Australia, including some parts of Asia and the Western Pacific region, during JE virus transmission season
people who live or work on the outer islands of Torres Strait.

See the recommendations in the Australian Immunisation Handbook JE chapter for further details.

* Your state or territory will determine if an individual is in a risk region and is eligible to receive JE vaccination. For more information, refer to the following state and territory-specific webpages: Australian Capital Territory (ACT), New South Wales (NSW), Northern Territory (NT), Queensland (Qld), South Australia (SA), Tasmania (Tas), Victoria (Vic), Western Australia (WA).

Who can administer JE vaccines?

Immunisation providers who are authorised to administer JE vaccines vary by state and territory. Depending on specific jurisdictional legislation, they may include general practitioners, pharmacists and/or nurse immunisers.

For more information, refer to the state and territory webpages:

Is JE vaccination recommended before travel?

JE vaccination is recommended for people who are travelling to a JE risk region of Australia who may be bitten by mosquitoes. For information on risk regions, refer to state and territory guidance. Risk regions may change depending on where JE virus is detected.

JE vaccination is also recommended for long-term travellers (e.g. more than one month) to certain regions outside Australia during the JE virus transmission season. Short-term travellers can also consider vaccination if there are specific risk factors, such as visiting rural or agricultural areas or engaging in considerable outdoor activities.

More information on recommendations for travellers can be found in the Australian Immunisation Handbook.

Which JE vaccines are available?

There are two JE vaccines available in Australia:

Imojev
JEspect (also known as Ixiaro).

Both vaccines are safe and effective. Which vaccine is recommended will depend on the individual’s age, pregnancy status and immunocompromising status as well as availability.

Imojev is available for people aged 9 months and over. However, pregnant women and immunocompromised people cannot receive Imojev, as it is a live vaccine. Women should avoid pregnancy for 28 days after vaccination with Imojev.

JEspect is available for people aged 2 months and over. It is recommended for pregnant women, immunocompromised people and children aged 2 months to less than 9 months – none of whom can receive Imojev.

The Australian Immunisation Handbook JE chapter includes more information on vaccines, dosage and administration.

Are there age-specific dose requirements for JEspect vaccine?

The primary vaccination schedule for JEspect consists of two doses administered 28 days apart, and the dosage depends on the age of the person:

infants and children aged 2 months to less than 3 years should receive 0.25 mL per dose.
children aged ≥3 years and adults should receive 0.5 mL per dose.

The vaccine comes as a pre-filled syringe that contains 0.5 mL. When administering a dose of JEspect, immunisers should draw up 0.25 mL and discard the remaining half-dose.

Can pregnant or breastfeeding women receive the JE vaccine?

Yes, pregnant women can receive two doses of the JEspect vaccine only.

Pregnant women cannot receive the Imojev vaccine, since it is a live attenuated vaccine and these vaccines are generally contraindicated in pregnant women. Women should avoid pregnancy for 28 days after vaccination with Imojev.

No safety concerns have been identified regarding the administration of the JEspect vaccine during pregnancy, although data are limited.

Women who are breastfeeding are recommended to receive JEspect; however, Imojev can be given.

The Australian Immunisation Handbook JE chapter includes more information on vaccines, dosage and administration.

Are the JE vaccines interchangeable between the first dose and the second dose?

The Imojev vaccine only requires one dose for the primary course.

The vaccine registered as JEspect in Australia is registered as Ixiaro in some countries. Ixiaro is an equivalent product and JEspect and Ixiaro can be given interchangeably. ATAGI recommendations on the use of Ixiaro are equivalent to those for JEspect.

The JEspect and Ixiaro vaccines are not interchangeable with the Imojev vaccine. If the first dose of JEspect or Ixiaro has been administered, JEspect or Ixiaro vaccine should be given as the second dose.

If a JE vaccine has been administered overseas and the relevant vaccine is not available in Australia, either Imojev or JEspect can be administered if there is an ongoing risk of exposure to JE virus.

The Australian Immunisation Handbook includes more details on the interchangeability of JE vaccines.

Are booster doses required? If so, who should receive a booster dose?

Yes, some people may require a booster dose of either Imojev or JEspect vaccine.

If a person is recommended to receive JE vaccination and it has been more than one year since they completed the primary JE vaccine course, a booster dose is recommended if the person is still at risk of exposure to JE virus.

An exception is if there is evidence that the person has previously received a dose of Imojev vaccine when they were aged 18 years or over. In this case, a booster dose is not required.

If possible, the same vaccine used in the primary course should be used as the booster dose, given that Imojev and JEspect vaccines are not considered interchangeable. However, using a different vaccine brand for the booster dose should produce a good immune response and there are no identified safety concerns.

Is serology (blood) testing required before JE vaccination?

No, blood testing is not required before receiving JE vaccination.

If a person has evidence of antibodies to the JE virus, the vaccine can still be administered.

Can JE vaccines be co-administered with (i.e. given at the same time as) other vaccines?

Yes, Imojev and JEspect vaccines can be co-administered with other indicated vaccines. If a JE vaccine is being co-administered with another vaccine, it is recommended to administer the vaccines in different limbs.

Given Imojev is a live attenuated vaccine, it should be administered 4 weeks apart from other live vaccines, if the vaccines are not administered at the same time.

The Australian immunisation Handbook includes more information on the co-administration of JE vaccines and other vaccines.

How is the safety of JE vaccines monitored?

In Australia, the Therapeutic Goods Administration (TGA) assesses the quality of every batch of vaccine, including JE vaccines, before it is distributed in Australia. The TGA also collects, analyses and reports data on adverse events after vaccination once a vaccine is in use.

Individuals and healthcare providers can also report adverse effects directly to the TGA.

How do I report JE vaccines to the Australian Immunisation Register (AIR)?

All JE vaccines given should be reported to the AIR.

Immunisation providers can report vaccination encounters via their practice management software or directly to the AIR site. Information for providers about how to record and update immunisation details is available on the Services Australia website.

All individuals, including those without a Medicare card, can have vaccines recorded on the AIR.