Does the Vaccine Effectively Prevent Japanese Encephalitis Infection?

September 9, 2021 | Written By: Nabil Nur Aiman Jasman

Japanese Encephalitis (JE) is a viral infection caused by Japanese Encephalitis virus. The virus that causes JE transmission comes from the Flavivirus group and JE is a zoonotic disease, meaning the disease transmitted to humans by animals. The vector of this virus is the Culex mosquito. The virus will first infect the mosquitoes and then infect pigs, birds and other animals before infecting humans especially those working in farms, paddy fields and rural areas. The incubation period of the JE virus before the infected patient shows signs and symptoms is between 5 to 15 days. So far, there is no solid evidence that this virus can be transmitted from human to human.

Japanese Encephalitis Vaccine

JE vaccine is a live-attenuated vaccine which contains a weakened living virus to stimulate the body's immune system to produce antibodies. This lowers the risk of getting complications caused by JE when exposed to this virus in the future.

There are several pharmaceutical companies responsible for producing Japanese Encephalitis vaccines and each company uses a different brand such as IXIARO and IMOJEV. In Malaysia, the JE vaccine we are using is IMOJEV.

In our country, only babies born in Sarawak are given the JE vaccination. Vaccine JE in Sarawak given in 2 doses, at the age of 9 and 21 months based on the National Immunization Schedule.

Importance of Japanese Encephalitis Vaccine

JE vaccination is given to the residents in endemic areas during infanthood and to those who are traveling to the endemic areas. This is because there is still no special treatment for JE and this infection can happen throughout the year, especially in Malaysia which is in the tropics and equatorial climate. The World Health Organization (WHO) reports that there are 50,000 to 60,000 cases of Japanese Encephalitis reported each year and that there are 13,000 to 20,000 deaths reported. JE not only causes complications such as permanent disability to the brain and limbs but can also cause death due to inflammation of the brain and several other complications. Therefore, the Ministry of Health Malaysia has included the JE vaccine in the national immunization schedule specifically for those who are living in Sarawak. How well do you know about vaccines? Find out here.

Signs and Symptoms of Japanese Encephalitis

Most individuals infected with the JE virus are asymptomatic or only experience mild symptoms. However, some individuals can get more serious symptoms and complications such as inflammation in the lining of the brain which can be fatal. The following are the signs and symptoms that may occur in individuals infected with the JE virus:

  • High grade fever

  • Chills and rigors

  • Headache

  • Neck stiffness

  • Nausea and vomiting

  • Stomachache

  • Mental disorders such as confusion and behavioral change

  • Muscle and joint pain

  • Fatigue

  • Weight loss

Complications of JE Infection

JE infection can cause some complications such as:

  • Seizure

  • Personality changes

  • Paralyzed or weakened limbs

  • Learning problems among children

  • Secondary bacterial infections (pneumonia and urinary tract infections); related to supportive treatment

Japanese Encephalitis Treatment

Currently, there is no specific treatment for Japanese Encephalitis. All patients infected with the JE virus will receive supportive treatment to relieve fever, muscle aches and pains, neurological problems and continuous hydration.

According to the United Kingdom National Health Service (NHS), 1 in 3 people with JE die due to developing serious complications. The healing rate can take weeks to months and nearly half of the patients who recover from JE experience permanent disability due to damage to the spinal cord and brain. 

Who Need to Take JE Vaccination

Apart from Malaysia, JE is endemic in most Asian countries such as India, Sri Lanka, China, Korea, Japan, Thailand, Cambodia, the Philippines and Indonesia. Each country has Guidelines Japanese Encephalitis of their own to provide immunization or prevention methods to deal with this infection among the population of their country.

People who need to take JE immunization are:

  • Residents in JE endemic areas

  • People travelling to the JE endemic areas and spending more than a month in the area or country

  • Laboratory workers expose to JE virus

Precautions Prior To Vaccination

  • Infants or individuals who experienced life-threatening allergic reactions after taking JE vaccine does not need to take the second dose of the vaccine

  • Baby or individual who may have life-threatening allergies by the ingredients contained in the JE vaccine do not need to take the vaccination

  • Pregnant mother. No studies on the effects of JE vaccination on pregnant mothers have been performed. It is best to delay the vaccination first. However, pregnant mothers who need to go to the JE endemic area for unavoidable reasons may be given an injection of JE vaccine after taking into account the pros and cons that may occur. Any decision made should be properly discussed with the mother and Obstetric & Gynaecology doctor attending her.

  • If you or your child has experienced any problems with the vaccine, be sure to tell your doctor about the history of allergies and problems you have had before taking the injection.

Side effects of the JE vaccine

Here are some side effects of the JE vaccine injection:

  • Fever

  • Fatigue

  • Chills

  • Rash, itching and swelling at the injection site

  • Headache

  • Dizziness

  • Joint and muscle pain

  • Runny nose

  • Cough

  • Shortness of breath

  • Abdominal pain

  • Nausea and vomiting

  • Diarrhea

Usually, side effects of JE vaccination are self-limiting and will heal in a short time. Please refer or seek medical attention to the nearest clinic or hospital in case you or your child developed serious symptoms after the injection.

Prevention of JE

Precautions should be taken by everyone in preventing Japanese Encephalitis from spreading. Here are some steps you can take to prevent yourself and your family and community from the JE outbreak:

  • Get a Japanese Encephalitis vaccine if you will be living in a JE endemic area for more than a month

  • If  you are sleeping with windows open, it is recommended to use nets

  • Using mosquito repellent and insecticide spray

  • Destroy mosquito breeding sites and keep the surrounding area clean

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