Encephalitis Vaccine is used for active immunization to protect against Japanese encephalitis in adults, adolescents, children, and infants aged 2 months and above. It is recommended for individuals who may be at risk of exposure, such as travelers to endemic areas or people whose occupations increase their risk.

The exact mechanism of action of Japanese encephalitis vaccines is not fully understood. However, animal studies suggest that the vaccine stimulates the immune system to produce antibodies against the Japanese encephalitis virus, which provide protection. Experimental studies in mice treated with human vaccine-derived antibodies showed that most mice with a neutralizing antibody titre of at least 1:10 were protected from a fatal viral challenge.

Adults (18 to ≤ 65 years of age): The primary vaccination series consists of two separate doses of 0.5 ml each, according to the following conventional schedule:

• First dose: Day 0.
• Second dose: 28 days after first dose.

Rapid schedule: Persons aged 18 to ≤65 years can be vaccinated in a rapid schedule as follows:

• First dose: Day 0.
• Second dose: 7 days after first dose.

With both schedules, primary immunisation should be completed at least one week prior to potential exposure to Japanese encephalitis virus (JEV). It is recommended that vaccinees who received the first dose of Encephalitis Vaccine complete the primary 2-dose vaccination course with Encephalitis Vaccine. If the primary immunization of two injections is not completed, full protection against the disease might not be achieved. There is data that a second injection given up to 11 months after the first dose results in high seroconversion rates.

Booster dose: A booster dose (third dose) should be given within the second year (i.e. 12-24 months) after primary immunization, prior to potential re-exposure to JEV. Persons at continuous risk for acquiring Japanese encephalitis (laboratory personnel or persons residing in endemic areas) should receive a booster dose at month 12 after primary immunization. Long-term seroprotection data following a first booster dose administered 12-24 months after primary immunization suggest that a second booster should be given 10 years after the first booster dose, prior to potential exposure to JEV.

Elderly (>65 years of age): The primary vaccination series consists of two separate doses of 0.5 ml each, according to the following conventional schedule:

• First dose: Day 0.
• Second dose: 28 days after first dose.

Pediatric Population:
Children and adolescents from 3 years to <18 years of age: The primary vaccination series consists of two separate doses of 0.5 ml according to the following schedule:

• First dose: Day 0.
• Second dose: 28 days after first dose.

Children from 2 months to <3 years of age: The primary vaccination series consists of two separate doses of 0.25 ml according to the following schedule:

• First dose: Day 0.
• Second dose: 28 days after first dose.

Administration: The vaccine should be administered by intramuscular injection into the deltoid muscle. In infants, the anterolateral aspect of the thigh may be used as injection site. Encephalitis Vaccine should never be injected intravascularly. When Encephalitis Vaccine is administered concomitantly with injectable vaccines, they should be given with separate syringes at opposite sites. Exceptionally, Encephalitis Vaccine can also be administered subcutaneously to patients with thrombocytopenia or bleeding disorders since bleeding may occur following an intramuscular administration. Subcutaneous administration could lead to a suboptimal response to the vaccine. However, it should be noted that there are no clinical efficacy data to support administration by the subcutaneous route.

Encephalitis Vaccine should not be used in individuals who are hypersensitive to the active substance, any of its excipients, or residual components such as protamine sulphate, formaldehyde, bovine serum albumin, host cell DNA, sodium metabisulphite, or host cell proteins. Individuals who develop hypersensitivity reactions after the first dose should not receive a second dose. Vaccination should also be postponed in individuals with acute severe febrile illness.

Very common side effects include:  headache, muscle pain, injection site pain, tenderness, and fatigue.

Common side effects include:  nausea, flu-like illness, fever, and local injection site reactions such as redness, swelling, hardness, or itching.

Uncommon side effects may include:  vomiting, rash, swollen lymph nodes, migraine, dizziness, vertigo, diarrhea, abdominal pain, excessive sweating, itching, chills, general malaise, joint or muscle stiffness, weakness, and abnormal liver function test results.

Pregnancy: Data on the use of Encephalitis Vaccine in pregnant women are limited. Animal studies have shown findings of uncertain clinical relevance. As a precaution, its use during pregnancy should be avoided.

Breast-feeding: It is unknown whether the vaccine is excreted in human milk. Although significant exposure in breastfed infants is not expected, its use during lactation should be avoided due to lack of sufficient data.

Fertility: Animal studies have not shown any harmful effects on female fertility, fetal development, or offspring survival.

The safety and effectiveness of Encephalitis Vaccine in children younger than 2 months have not been established, and no data are available.

Vaccines, Anti-sera, and Immunoglobulins.

Store in a refrigerator at 2°C to 8°C. Do not freeze. Keep in the original packaging to protect from light.