Japanese Encephalitis and the Japanese Encephalitis Vaccine

Planning on traveling from Australia to PNG, or anywhere in Asia? You may encounter mosquitoes that transmit Japanese encephalitis, a dangerous and potentially fatal illness.

Thankfully there is an effective Japanese encephalitis vaccine that you can receive before you depart which can dramatically reduce your chances of getting seriously ill.

While the virus is mostly found in rural areas, you may be strongly recommended by your doctor to receive a vaccination for Japanese encephalitis even if you’re planning to remain in cities.

There are two available Japanese encephalitis vaccinations. Before your next visit to Asia, here’s everything you should know about this important vaccination.

What is the Japanese Encephalitis Vaccination?

There are two available Japanese Encephalitis vaccines: the inactivated virus vaccine, known as JEspect, and the attenuated live viral vaccine, known as Imojev.

JEspect is given in two intramuscular doses, with the second dose occurring 28 days after the first. It is licenced for use in individuals over the age of 18 years, but it can also be used from the age of 2 months if required and with consideration. A booster after 12-24 months should be given if required due to ongoing exposure.

If adults are considered at imminent risk of infection, an accelerated schedule can be followed with two doses given seven days apart.

JEspect is considered 96% effective after two doses 28 days apart.

Imojev is given in a single subcutaneous dose and considered 94% effective after 14 days. For children aged 9 months to 18 years, a booster can be delivered after 1-2 years if required. Boosters are not required for adults over 18 years old.

When possible, Imojev is recommended over JEspect for anyone being vaccinated for this disease. As this vaccine is a live attenuated viral vaccine, it cannot be used in places where live vaccines are contraindicated.

Who Should Get the Japanese Encephalitis Vaccine?

Your medical provider will give you specific guidance on whether you should receive the Japanese encephalitis vaccination before you travel. Usually the vaccine is recommended in the following cases:

  • The Japanese encephalitis vaccine is most highly recommended for anyone traveling for one month or longer to endemic areas in Asia and Papua New Guinea, especially during the virus transmission season.
  • If your visit will be less than one month, you may still need to get the JE vaccine. Consider if your travel will occur during the wet season, if you’ll be visiting at-risk areas, if you’ll be outdoors frequently, and if you’re staying in accommodations without screens, air conditioning, or bed nets.
  • JE vaccines are also recommended for laboratory workers who might be exposed to the JE virus and people who live or work on the outer islands of Torres Strait.

Who Shouldn’t Get the Vaccine?

The Japanese encephalitis vaccine (Imojev) which is live attenuated, is not recommended for those who are pregnant or breastfeeding, have acute febrile illness, and are immunocompromised.

The JE vaccine is just one way to combat the virus. More importantly, the biggest step to preventing JE transmission is by avoiding mosquitos and mosquito bites. All travellers should utilise repellents and protective clothing.

Vaccination Side Effects or Reactions

In studies, approximately 40% of subjects receiving either of the JE vaccinations experienced reactions that mostly occurred and resolved within the first three days. Some of the most common side effects include headaches, muscular pain, flu-like illness, and fatigue. Other side effects may include:

  • Injection site redness, swelling, or itching is by far the most common.
  • As Imojev is a live attenuated vaccine, it can be associated with a mild fever or feeling as if you are coming down with a virus for up to 10 days after the vaccine delivery.

FAQs about Japanese Encephalitis and the JE Vaccine

Is Japanese encephalitis curable?

Currently, there is no cure for Japanese encephalitis. Typically, someone diagnosed with JE will be admitted to the hospital for symptom treatment.

Which countries have Japanese encephalitis?

Japanese encephalitis is found throughout the south-eastern world. The virus has been identified in areas such as Australia, Burma, China, India, Indonesia, Japan, Malaysia, Papua New Guinea, Singapore, Sri Lanka, Thailand, and Vietnam, among others.

What are the chances of getting Japanese encephalitis?

The chances of contracting Japanese encephalitis are small, at about 1 in a 1,000,000 chance. However, JE is a serious disease and once contracted, generally 1/3 of people will recover fully, 1/3 will have ongoing neurological issues and 1/3 will die from the disease.

How do you contract Japanese encephalitis?

Japanese encephalitis is contracted through mosquitos. Mosquitos become infected when they suck the blood of an animal or bird with JE, and then they pass the disease on to the humans they bite. It is spread mainly by night biting mosquitoes.

How do you prevent Japanese encephalitis?

The most effective way to prevent Japanese encephalitis is by avoiding contact with mosquitoes. Mosquitoes can bite during the day or night, so it’s important to consistently use insect repellent throughout your travels.

Treat your clothing and gear, and ensure you’ve gotten your vaccinations or booster before traveling. Wear long-sleeved shirts and long pants, and use screens and air conditioning in your accommodations.

What does Japanese encephalitis look like?

Symptoms of Japanese encephalitis typically don’t appear for 5-10 days after infection. The first symptoms typically include fever, vomiting, headache, confusion, and difficulty moving.

What is Japanese encephalitis?

Encephalitis is inflammation of the brain that can be caused by viral or bacterial factors. Japanese encephalitis is a viral infection of the brain that can result in brain inflammation and swelling. JE virus is spread only through mosquito bites.

How long does Japanese encephalitis last?

Most cases of Japanese encephalitis have an incubation period of 2-26 days, and typically, cases resolve in a few days or weeks. Some remain unwell for long periods and may have ongoing neurological issues. As mentioned many also die from the infection.


It usually takes from four to 14 days for symptoms such as fever, muscle aches, and severe headache to develop. In some people, symptoms may progress to include stiffness of the neck and eventually coma, which can result in death or irreparable brain damage.

For travellers there is a very low risk of being infected but the consequences of the disease can be high. Japanese encephalitis can result in death and brain damage in a significant proportion of those developing the disease.


The first line of defence against Japanese encephalitis is avoiding mosquito bites. Two new vaccines are available and both are very effective in prevention. One vaccine is a ‘live’ single-dose formula which protects individuals for several years. The second vaccine involves a course of two injections over a month, then a booster every two to three years if risk is on- going. Both Japanese encephalitis vaccines are suitable for children as young as 12 months.