Japanese Encephalitis Vaccine - An Overview

What Is the Japanese Encephalitis Virus?

Japanese encephalitis is a virus related to yellow fever, dengue, and West Nile, spreading through mosquitoes. The mode of spread is through the bite of an infected mosquito which is transmitted to humans. The transmission occurs in summer and early fall, from May to September. Japanese encephalitis virus occurs in many parts of the world, like Korea, South Asia, Japan, the Indian subcontinent, parts of Oceania, and other rural areas.

What Are the Symptoms of the Japanese Encephalitis Virus?

Symptoms of the Japanese Encephalitis virus are as follows:

• Fever.

• Tremor (nervous system disorder that causes shaking or involuntary shaking).

• Disorientation.

• Headache.

• Coma (prolonged unconsciousness caused by trauma to the brain).

• Convulsion (uncontrolled muscle contraction).

• Seizures.

• Weakness.

• Vomiting.

• Difficulty in movement.

How to Diagnose Japanese Encephalitis Virus?

Individuals who live in high-risk Japanese encephalitis virus endemic (disease spread or localized to a particular area) areas are prone to get affected by this virus. Laboratory tests such as identification of specific Immunoglobulin M (IgM) antibodies in a single sample of cerebrospinal fluid (CSF) or serum using an IgM-capture Enzyme-Linked Immunosorbent Assay (ELISA). The test is likely to be positive only in the early stages of infection.

Which Countries Are at Higher Risk of Japanese Encephalitis Virus?

Japanese encephalitis occurs in many parts of Asia and beyond it, namely :

• China.

• Indonesia.

• Malaysia.

• Sri Lanka.

• The Philippines.

• Nepal.

• India.

• Laos.

• Cambodia.

• Vietnam.

• Thailand.

• Myanmar.

How Common Is Japanese Encephalitis?

It is rare for travelers to visit high-risk countries affected by the virus for a short span of time. The estimation of Japanese encephalitis data by the World Health Organisation reports 68,000 cases of Japanese encephalitis worldwide each year. The people who live as well as work in rural areas involving pig farms and rice fields are at higher risk for this virus. Approximately 75 % of cases involve children under 15 years of age.

What Are Vaccines?

The vaccine is a weakened suspension of killed and fragmented microorganisms of physical preparation consisting of antibiotics, lymphocytes, or messenger RNA (mRNA) administered in the primary stage inorder to prevent disease. A British physician named Edward Jenner in the year 1796 used the cowpox virus for protection against smallpox. Later, French microbiologist Louis Pasteur 1885 developed the first vaccine against rabies. The vaccine helps in providing immunization to the body. It is a procedure for stimulating an immune response through active vaccination. They are usually found in the form of liquids, nasal sprays, pills, or injections.

What Is the Mechanism of Action of the Vaccine?

The immune system comprises tissues, cells, and organs that work together to invade the infection. Bacterial and virus cells in the body are marker cells known as antigens. Antigens can induce changes in the immune system and cause damage. When the vaccine enters the body, it guides the immune system to produce antibodies against the antigens. Vaccines consist of inactivated/ weakened forms of the virus or bacteria in the body.

Lymphocytes are white blood cells of the immune system that become active whenever foreign protein comes in contact with the antigen. When foreign microbes invade the human body, the immune system starts triggering a series of responses to identify and remove them from the body. The foreign microbes introduce antigens into the body, thus causing coughing, inflammation, sneezing, and fever as a means of protection by the immune system. Special cells such as B and T cells are responsible for fighting against the microbes by creating memory cells as a response. B-lymphocytes are one of the defensive white blood cells that have the ability to produce antibodies against microbes. At the same time, t-lymphocytes are memory cells that recognize the familiar germ to which the body was exposed previously. These immune cells recognize foreign invaders and produce specific antibodies.

What Is the Japanese Encephalitis Vaccine?

Japanese Encephalitis vaccine is manufactured as Inactivated Vero cell culture-derived Japanese encephalitis vaccine (IXIARO). The vaccine was approved for 17 years and older in March 2009 and for two months to sixteen years in May 2013. It is given in a two-dose series. Dose two is administered 28 days after the first dose. A booster dose can be taken after 11 months of the last scheduled dose. Both doses of vaccine should be administered seven days before visiting a place with a high risk of Japanese encephalitis virus.

What Is the Mode of Administration of the Japanese Encephalitis Vaccines?

The vaccine is administered by intramuscular injection into the anterolateral aspect of the thigh in infants aged 2 to 11 months old and deltoid muscle in individuals three years and older.

When to Get Japanese Encephalitis Vaccination?

The person should get the vaccination in the following cases:

• Planning to stay or planning stays in a high-risk country for months.

• Working in a microbiology laboratory with potential exposure to the virus.

• Going camping and cycling in high-risk areas of the country.

• Visiting rural areas such as rice fields and marshlands in a high-risk country.

What Are the Precautions Taken Before Vaccination?

An allergy that occurs from the drug should be taken into consideration before vaccination. In addition, the vaccine may not have efficacy in an immunodeficient person or one suffering from a bleeding disorder. The vaccination should be postponed in case of fever. It may not be recommended in case of pregnancy or breastfeeding.

What Are Side-Effects of the Japanese Encephalitis Virus?

The side effects of the Japanese encephalitis virus are:

• Headache.

• Muscle ache.

• Itching.

• Red, swelling, or lump at the site of injection.

• Chills.

• Cough.

• Diarrhea (refers to watery loose stools that occur more frequently than usual).

• Running nose.

• Hives (refers to a common skin rash that occurs as a result of medication, stress, or certain food).

• Fast heart rate.

• Dizziness.

• Sore throat.

• Skin rash.

• Shivering.

• Loss of appetite.

• Sweating.

• Trouble sleeping.

• Vomiting.

• Difficulty breathing.

• Sneezing.

What Are the Preventive Measures After Vaccination?

After vaccination as well, it is essential to have protection against mosquitoes. Methods to adopt for protection are:

• Wear loose, long-fitting clothes when outdoors.

• Applying effective insect repellent cream on exposed skin.

• Avoid containers filled with water, as they can serve as breeding grounds for mosquitoes.

• Use of insecticide in the rooms during summers and monsoons.

Conclusion:

Japanese encephalitis is a viral infection found in birds and pigs and is then passed to mosquitoes when they bite an infected animal. There is exactly no cure for this virus. Precaution involves self-care and vaccination prior to travel. Treatment involves supporting the function of the body through oxygen, fluid, and medication to treat any symptoms.