Medicine overview
Indications of Imojev
Imojev is indicated for active immunization against Japanese encephalitis virus (JEV), the mosquito-borne flavivirus that is the most common vaccine-preventable cause of viral encephalitis in South and Southeast Asia, including Bangladesh.
Established/Approved Uses
- Routine immunization of infants and children in Japanese encephalitis-endemic areas, in accordance with national Expanded Programme on Immunization (EPI) schedules.
- Pre-exposure immunization of travelers who plan an extended stay (generally ≥1 month) in endemic rural areas, or shorter stays with high-risk activities (e.g., extensive outdoor exposure, agricultural work).
- Laboratory workers with potential exposure to live JEV.
Guideline-Supported / Adjunct Use
- Booster dosing in previously vaccinated individuals who remain at ongoing risk of exposure, per WHO and national immunization guidance.
Imojev does not protect against other causes of encephalitis (e.g., herpes simplex virus, other arboviruses) and is not indicated for treatment of active infection.
Composition
Each dose of Encephalitis Vaccine contains inactivated or live-attenuated Japanese encephalitis virus antigen (strain and potency vary by manufacturer/presentation), together with stabilizers and, for inactivated formulations, an adjuvant. Some presentations are supplied as a lyophilized powder with a separate diluent for reconstitution; others are supplied as a ready-to-use liquid suspension for injection. Refer to the specific product label for exact strain, antigen content, and excipients.
Description
Imojev is a vaccine used to stimulate active, protective immunity against Japanese encephalitis virus. It is administered by intramuscular or subcutaneous injection depending on the specific product, and works by exposing the immune system to viral antigen so that protective antibodies are generated before natural exposure to the virus occurs.
Imojev is used both in national childhood immunization programs in endemic countries and for pre-travel prophylaxis in non-immune individuals traveling to endemic regions.
Therapeutic Class
Imojev belongs to the therapeutic class of viral vaccines, specifically inactivated or live-attenuated Japanese encephalitis virus vaccines, used for active immunization/immunoprophylaxis.
Pharmacology
Mechanism
Encephalitis Vaccine works by presenting Japanese encephalitis virus antigen to the immune system, inducing production of neutralizing antibodies and a memory immune response, without causing the disease itself (in the case of inactivated formulations) or by causing a controlled, attenuated infection that mimics natural immunity (in the case of live-attenuated formulations).
Protective antibody titers typically develop within 2-4 weeks after completion of the primary vaccination series, and immunity may wane over time, which is why booster doses are recommended for individuals with ongoing risk of exposure.
Dosage & Administration of Imojev
Adult Dose
| Indication | Regimen |
|---|---|
| Primary immunization (inactivated formulation) | Two doses given intramuscularly, 28 days apart; a booster dose may be given approximately 1-2 years later if ongoing exposure risk continues. |
| Primary immunization (live-attenuated formulation) | A single dose given subcutaneously, per the specific product's approved schedule. |
Pediatric Dose
Schedules and minimum ages vary by specific product; consult the national EPI schedule and the specific product label. In general, primary immunization can begin from 2 months of age (product-dependent), with dose volume sometimes reduced for younger infants. See Pediatric Uses for details.
Administration
Imojev is administered by a trained healthcare professional as an intramuscular or subcutaneous injection (route depends on the specific formulation); it is not for intravenous administration. Administer immediately after reconstitution where applicable (see Reconstitution).
Administration of Imojev
Imojev should be given only by a qualified healthcare professional under conditions where treatment for a rare acute anaphylactic reaction is available. Do not administer intravenously. If supplied as a lyophilized powder, reconstitute only with the diluent provided and use promptly (see Reconstitution). Inspect the vaccine visually for particulate matter or discoloration before administration.
Interaction of Imojev
Imojev may be administered concomitantly with other age-appropriate inactivated or live vaccines, at separate injection sites, in accordance with national immunization schedules.
- Immunosuppressive therapy (corticosteroids, chemotherapy, biologics): may reduce the immune response to Imojev; immunocompromised individuals may have a suboptimal antibody response, and live-attenuated formulations should generally be deferred in significantly immunosuppressed individuals (see Contraindications).
- Immunoglobulins/blood products: recent administration of antibody-containing blood products may interfere with the immune response to live-attenuated formulations; spacing per standard immunization guidance is advised.
Contraindications
Encephalitis Vaccine is contraindicated in individuals with:
- A history of severe allergic reaction (e.g., anaphylaxis) to a previous dose of Encephalitis Vaccine or to any component of the vaccine.
- A known severe hypersensitivity to any vaccine excipient (e.g., certain formulations contain protamine sulfate or other specific excipients to which the recipient is known to be allergic).
For live-attenuated formulations specifically, severe immunodeficiency is an absolute contraindication. Moderate-to-severe acute illness (with or without fever) is a reason to defer vaccination rather than a permanent contraindication.
Side Effects of Imojev
Most reactions to Imojev are mild and self-limited.
Common
- Injection-site pain, redness, or swelling
- Mild fever
- Headache, myalgia, fatigue
Uncommon/Rare
- Generalized rash or urticaria
- Lymphadenopathy
- Rarely, immediate hypersensitivity reactions including anaphylaxis (see Contraindications and Precautions)
Pregnancy & Lactation
Pregnancy: Data on the use of Imojev in pregnancy are limited. As a general precaution, and particularly for live-attenuated formulations, Imojev should be used during pregnancy only if clearly needed and the potential benefit justifies the potential risk to the fetus; a physician should be consulted before administration in pregnancy, and vaccination should generally be deferred to the postpartum period when travel or exposure timing allows.
Lactation: There is no specific evidence that Imojev is unsafe during breastfeeding; a physician should be consulted to weigh individual benefit against any theoretical risk before administration to a breastfeeding mother.
Precautions & Warnings
- Have appropriate medical treatment (including epinephrine) available in the event of a rare anaphylactic reaction following administration of Imojev.
- Defer administration of Imojev in individuals with moderate or severe acute illness until they have recovered.
- Use caution in individuals with a history of egg allergy or gelatin allergy, as some Imojev presentations are manufactured using egg-based substrates or contain gelatin stabilizer; consult the specific product label.
- Imojev does not provide 100% protection; travelers should also be counseled on mosquito-bite avoidance measures.
- See Contraindications for individuals in whom Imojev must not be given, and Use in Special Populations for guidance on immunocompromised individuals.
Overdose Effects of Imojev
There is no established scenario of clinically meaningful "overdose" with Imojev, as it is administered as discrete, scheduled doses by a healthcare professional rather than self-administered on an ongoing basis. If an excessive dose or dosing error is suspected, or if a recipient develops any concerning symptoms after receiving Imojev, seek immediate medical attention or contact a poison control center/emergency services rather than attempting home management.
Storage Conditions
Store Imojev in the refrigerator between 2°C and 8°C; do not freeze. Protect from light. Once reconstituted (where applicable), use immediately or within the timeframe specified by the manufacturer. Keep out of reach of children.
Use In Special Populations
Immunocompromised Individuals
Live-attenuated formulations of Imojev are generally contraindicated in individuals with significant immunosuppression (e.g., advanced HIV disease, active malignancy on chemotherapy, high-dose corticosteroid therapy, congenital immunodeficiency); inactivated formulations may be used but may produce a reduced immune response, and specialist consultation is advised.
Elderly
Imojev may be given to elderly individuals at risk of exposure; no specific dose adjustment is established, though immune response may be somewhat reduced with advancing age.
Renal/Hepatic Impairment
No specific dose adjustment of Imojev is established for renal or hepatic impairment.
Duration Of Treatment
Imojev is not a continuous treatment but a scheduled immunization course: either a single dose or two doses 28 days apart depending on the specific formulation, followed by a booster dose after approximately 1-2 years (and periodically thereafter) for individuals with ongoing risk of exposure. Duration of protective immunity varies by product; follow national immunization guidance for booster timing.
Reconstitution
Lyophilized (freeze-dried) presentations of Imojev must be reconstituted immediately before use, using only the diluent supplied with that specific product. Withdraw the diluent into a sterile syringe, inject it into the vial containing the lyophilized vaccine, and gently swirl (do not shake vigorously) until the powder is fully dissolved and the solution is clear or as described on the product label. Use the reconstituted vaccine promptly, within the time window specified by the manufacturer, and discard any unused portion. Ready-to-use liquid presentations of Imojev do not require reconstitution.
Drug Classes
Encephalitis Vaccine is classified as a viral vaccine (inactivated or live-attenuated Japanese encephalitis virus vaccine) within the broader category of immunizing biological products.
Mode Of Action
Encephalitis Vaccine acts by delivering Japanese encephalitis viral antigen to the immune system, stimulating both humoral (neutralizing antibody) and cell-mediated immune responses. This primes the immune system so that, upon subsequent natural exposure to Japanese encephalitis virus, a rapid and protective secondary immune response can occur, reducing the risk of clinical disease.
Pediatric Uses
Imojev is a key component of national childhood immunization programs in Japanese encephalitis-endemic countries, including Bangladesh's Expanded Programme on Immunization. Approved minimum age and schedule depend on the specific product; many inactivated formulations are approved from 2 months of age, while some live-attenuated formulations are approved from 8-9 months of age, generally coinciding with or shortly after the measles-containing vaccine dose. Dose volume may be reduced for younger infants for certain products. Safety and efficacy of specific presentations in neonates and in infants below the approved minimum age have not been established; consult the specific product label and national EPI guidance before administering Imojev outside the approved age range.
Frequently Asked Questions
Q: What is Imojev 0.5 ml/vial SC Injection used for?
A: Imojev 0.5 ml/vial SC Injection is used to actively immunize children and at-risk adults against Japanese encephalitis virus, a mosquito-borne virus that can cause serious brain infection. It is used both in routine childhood immunization programs and for pre-travel protection before visiting endemic areas.
Q: How many doses of Imojev 0.5 ml/vial SC Injection are needed?
A: Depending on the specific formulation, Imojev 0.5 ml/vial SC Injection is given as either a single dose or as two doses 28 days apart, with a booster dose recommended after about 1-2 years for people who remain at ongoing risk of exposure. Your physician will advise the exact schedule for the product being used.
Q: Is Imojev 0.5 ml/vial SC Injection safe during pregnancy?
A: Imojev 0.5 ml/vial SC Injection should be used during pregnancy only if clearly needed, since data in pregnant women are limited and potential benefit must be weighed against potential risk to the fetus; a physician should be consulted before Imojev 0.5 ml/vial SC Injection is given during pregnancy, and vaccination is often deferred until after delivery when possible.
Q: What are the common side effects of Imojev 0.5 ml/vial SC Injection?
A: The most common side effects of Imojev 0.5 ml/vial SC Injection are mild injection-site pain, redness or swelling, and low-grade fever. Serious allergic reactions are rare but can occur, which is why Imojev 0.5 ml/vial SC Injection should always be given in a setting where such reactions can be promptly treated.
Q: Who should not receive Imojev 0.5 ml/vial SC Injection?
A: Imojev 0.5 ml/vial SC Injection should not be given to anyone who has had a severe allergic reaction to a previous dose of Imojev 0.5 ml/vial SC Injection or to any of its components. Live forms of Imojev 0.5 ml/vial SC Injection should not be given to people with severe immune suppression, and vaccination should be postponed during moderate or severe acute illness.
Q: Can Imojev 0.5 ml/vial SC Injection be given with other vaccines?
A: Yes, in most cases Imojev 0.5 ml/vial SC Injection can be given at the same visit as other age-appropriate vaccines, using separate injection sites, following the national immunization schedule; your physician or immunization provider will confirm appropriate co-administration.
Disclaimer
The information provided is accurate to the best of our knowledge, but it does not replace professional medical advice. We cannot guarantee its completeness or accuracy, and the absence of specific information about a drug should not be taken as an endorsement. We are not responsible for any consequences arising from this information, so please consult a healthcare professional for any concerns or questions.
