FAQs

Japanese encephalitis (JE) is a potentially serious disease caused by the JE virus. The virus is spread by mosquito bites. It mainly occurs in Asia. JE virus is part of a group of viruses that can cause brain swelling (encephalitis). There are no treatments that can help your body fight the JE virus once you have it.¹ But there are ways to prevent JE.

Most people who get the JE virus don’t feel sick. Only about 1 in 250 people (less than 1%) infected with the virus have signs of sickness (symptoms).² If you do get symptoms, JE can be very serious, even if you’re young and healthy.

Symptoms usually show up 5 to 15 days after a bite from an infected mosquito. They may include:

• Fever
• Headache
• Nausea and vomiting
• Fatigue (tiredness)

People with serious infection may show symptoms of brain swelling (encephalitis) such as:

• Severe headache
• Neck or back stiffness
• Sensitivity to light
• Confusion
• Seizures (fits)
• Coma

Some people with serious illness develop paralysis (they can’t move some or all of their body). This can affect different parts of the body, including the lungs. If this happens, the person might need a machine (ventilator) to help them breathe.

Serious illness can lead to death. Survivors of JE may have long-term health issues, like trouble with memory, speech, or movement.

The JE virus is only spread to humans through bites from infected mosquitoes.³ You can’t get JE from another person, or from food. Once a person is infected, they can’t pass the virus to mosquitoes or other animals. Mosquitoes get the virus by biting infected animals such as pigs, and water birds like herons and egrets. The mosquitoes that spread JE virus are called Culex mosquitoes. Culex mosquitoes are most active at night, from dusk to dawn. For a short video that explains how a person can get the JE virus (JEV), see here.

JE occurs in 24 countries, mainly in Asia. It’s named after Japan, where it was first found. But it has been in many parts of Asia for a long time. JE is more common in rural areas, but it can happen anywhere the right mosquitoes and animals are found. In Asia, cases are often linked to rice farming areas. In some areas, cases peak in summer and autumn. In other areas, cases happen all year, often with a peak during the rainy season. Since 2021, cases have been reported in parts of mainland Australia.⁴ For a list of countries where JE is a risk and details on when the risk is highest, see here.

It is hard to know how many people get sick with JE. This is because most people who get it don’t get sick. If they do get sick, they don’t always get diagnosed. Even if they are diagnosed, this might not be reported to organisations that count cases of JE. Studies suggest about 100,000 people get JE around the world each year, and 25,000 people die from it.⁵

JE is rare in travellers. Only about one person per million who visits an area where there is a risk of JE will get sick with JE.⁶ But for travellers who go to risk areas during higher risk times, the risk may be two to five times higher than this.⁶

Anyone who travels to or lives in areas where JE is a risk can get JE. Your risk depends on where you go, what you do, how long you stay, and your age. The risk of getting sick from JE likely goes up as you get older. If you get JE and survive, scientists think you can not catch it again.⁷

In places where JE has been around for a long time, most people who get sick are children. This is because adults are often exposed as kids. After that their bodies learn how to prevent them from getting sick again (they become immune). Among travellers, more adults get sick because most have never been exposed and are not immune.

If you are spending a month or more in areas where JE is a risk, during times of the year when mosquito spread is more likely, the JE vaccine is recommended. If you are doing a shorter trip, you should still consider the vaccine, especially if your risk of exposure is higher.

The risk of getting JE while traveling may be higher if you:

• Travel for longer periods, or make more than one trip to risk areas
• Travel during times when being bitten by an infected mosquito is more likely
• Visit rural, farming or rice-growing areas
• Do outdoor activities like camping, hiking, trekking, biking or rafting
• Spend a lot of time outdoors, especially in the evening or night
• Stay in basic accommodation without air conditioning, window screens or bed nets

Your healthcare provider can help you understand your risk based on your situation and travel plans. You can also assess your risk using the JE risk tool at www.vaxical.com.

If a person has been in an area where JE can happen and shows signs of sickness (symptoms) like JE, their healthcare provider may test them for it. This is usually done with a test of their blood, or fluid from around their spine.⁸ If fluid from around the spine is needed, it will be taken out with a needle (lumbar puncture).

There are no treatments that can help your body fight JE.¹ Treatment focuses on helping you cope with the effects of the illness. Serious cases usually require hospital care and sometimes intensive care.

The best ways to prevent JE are to avoid being bitten by mosquitoes and getting vaccinated. There are two safe and effective JE vaccines available in Australia. They are called Imojev® and JEspect®. See “How can I avoid mosquito bites?” for tips on bite prevention.

Two JE vaccines are available in Australia: Imojev® and JEspect®.⁹ They are different types of vaccines, but both teach your immune system to fight the JE virus.

Imojev® is a live vaccine that contains a weakened form of the JE virus. It provides strong and long-lasting protection. It can be given to adults and children (9 months or older). However, it is not suitable for people with weakened immune systems or pregnant women. For those people, it could cause a serious infection. Imojev® is available in Australia, and in some parts of Asia.

JEspect® is a non-live (inactivated) vaccine. It is made with a killed version of the JE virus. It helps your immune system learn to recognise and fight the virus without causing illness. Several doses are usually needed for strong and lasting protection. It can be given to anyone aged 2 months or older. This includes people with weakened immune systems and pregnant women. JEspect® is available in Australia and New Zealand. In Europe and North America, it is known as Ixiaro.

JE vaccines work very well. There has never been a report of JE illness in a traveller who got the vaccine.^2,10

Because JE is not a common disease, we do not have studies that measure how well JE vaccines prevent illness. But we know what signs to look for to know if a vaccine works. Antibodies are proteins that help the body fight infections. If a vaccine causes people’s bodies to make antibodies that fight JE, this means the vaccine helps protect the person from JE.

In studies from Australia, Europe and the US:

• 95-99% of healthy adults showed signs of protection from JE (enough antibodies) one month after getting vaccinated with Imojev® (one dose) or JEspect® (two doses)^11,12
• 100% of healthy children showed signs of protection two months after receiving JEspect® (two doses)¹³

In a study from Thailand, 96% of children who had not previously had a JE vaccine showed signs of protection one month after receiving Imojev® (one dose).¹⁴

Older adults may not respond as well to vaccines.¹¹ For example, a study of the JEspect vaccine in adults aged 64 and older in Europe found that only 65% had signs of protection one month after receiving their second dose.¹⁵

Yes. Both vaccines available in Australia are safe and effective.⁹ They have been used for many years by travellers to southeast Asia, people living in the Torres Strait Islands, and Australian Defence Force personnel. Both vaccines, Imojev® and JEspect®, have been approved by the Therapeutic Goods Administration (TGA). Studies have not identified any safety issues, and they continue to be monitored for safety.

Imojev®is a live vaccine. It should not be given to people with weak immune systems, pregnant women, or children under 9 months, as it could cause a serious infection.

Feeling sick or sore (side effects) after a JE vaccine tend to be mild. They usually go away in three days or less. The most common side effects include pain, redness, or swelling where the vaccine is given (local reactions). People might also get a headache, muscle aches or fever. Severe reactions are very rare.

Both Imojev® and JEspect® have similar risks of side effects. These side effects are like those of other common vaccines. Children under 5 are more likely to have side effects than older children and adults. Adults more often report headaches and muscle aches. Children may more often have a fever.

In studies, about half of the people who got JE vaccines (44-68%) had side effects.^{12-14, 16,17} In all of these studies people had similar side effects whether they got a JE vaccine, another vaccine (for example hepatitis A) or an injection of a harmless substance (placebo).

In a study of 2750 Australians who got Imojev® or JEspect®, only 7% said they had side effects in the first five days after getting the vaccine.¹⁸ Most often they had some pain and swelling where they got the injection, felt tired, or had a headache.

After a JE vaccine, protection can last from one year to more than 5 years.⁹ How long the protection lasts depends on your age, how your body responds to vaccines, and which vaccine you got. If you’re staying in or going back to places where there’s a risk of JE, you might need to get another dose (called a booster) to stay protected for longer.⁹ If you got JEspect® as an adult, a booster dose is recommended after one year. If you had Imojev® as an adult, you don’t need a booster. For more information, see here.

Which vaccine you can get depends on your age, whether you are pregnant, and the health of your immune system.

People aged 9 months and older who are not pregnant and have normal immune systems can have either Imojev® or JEspect®. Women should wait for 28 days after getting Imojev® before trying to get pregnant.⁹

Pregnant women, people with weakened immune systems, and children aged 2 to 8 months can receive JEspect®. These groups should not have Imojev®, because it is a live vaccine.

JE vaccine is not required for entry to any country. See "Who should get JE vaccine?" for information on who the vaccine is recommended for.

For most people, JE vaccines are not paid for by the government (they are not included in the National Immunisation Program). Some Australians may qualify for free JE vaccine based on where they live or work, or the type of work they do. For more information, see “Who should get JE vaccine”.

Travellers usually have to pay for the vaccine themselves. The amount people have to pay may be different in different places. People can expect to pay about $100-150 per dose for JEspect®, or about $250-300 per dose for Imojev®. People need two doses of JEspect, but only one dose of Imojev® before a trip. So the total cost is similar for each option. You might also need to pay a fee to the healthcare provider who gives you the vaccine.

Yes. People can get either JE vaccine at the same time as other vaccines.¹⁹ If a person wants to get Imojev® and other live vaccines, they have two options. They can have Imojev® on the same day as other live vaccines. Or they can leave a gap of at least 28 days between the vaccines. Examples of other live vaccines include vaccines for measles-mumps-rubella (MMR), varicella (chickenpox), and Yellow fever (Stamaril®).

After getting a vaccine, your body needs time to respond before you are protected against the disease. This usually takes 2-4 weeks. You may also want to allow time so you do not have side effects from vaccines when you travel. It’s best to get travel health advice at least 6 weeks before your trip.  Remember, with Imojev®, you will only need one dose before you travel. If you get JEspect®, you will need two doses, given 1 to 4 weeks apart.

Whether you get a JE vaccine or not, it’s important to avoid mosquito bites. This will lower your chances of catching JE and other illnesses like dengue and malaria.

Here are some tips to protect yourself from mosquitos:

• Wear long-sleeved shirts and long pants outdoors
• Apply an insect repellent to any exposed skin
• Sleep in screened rooms or under a permethrin-treated bed net

Insect repellents that contain at least 20% DEET, 20% picaridin, or 30% OLE offer the best protection.²⁰ Check the label to see when to put them on again.

Wrist bands, patches and stickers are not a reliable way to prevent mosquito bites.

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This website has a glossary which can help explain unfamiliar terms (words). If you're still unsure, write down the term and ask your doctor or health professional next time you see them.

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