Imojev

Approved Indications:

A. Japanese Encephalitis (JE) Prevention:

• Primary vaccination for prevention of Japanese Encephalitis in individuals living in or traveling to endemic areas.
• For residents of endemic regions in Asia and the Western Pacific.
• For expatriates, military personnel, and frequent travelers spending ≥1 month in rural or agricultural areas where JE is prevalent.
• In laboratory workers or field personnel exposed to JE virus.
• Recommended for children living in endemic areas (typically aged ≥2 months depending on the vaccine type).

B. Booster Dose:

• For individuals previously vaccinated and still at risk of exposure, particularly if >1 year has passed since primary immunization.

Important Off-label or Clinically Accepted Uses:

• Pre-exposure vaccination in short-term travelers (<1 month) to endemic regions with expected high mosquito exposure or during JE outbreaks.
• In occupational exposure cases outside endemic regions for virologists working with JE virus in research or diagnostics.

Formulations:

• Inactivated (e.g., IXIARO® – derived from Vero cells)
• Live-attenuated (e.g., SA14-14-2 strain – widely used in Asia)

Route of Administration:

• Intramuscular (IM) for inactivated vaccines
• Subcutaneous (SC) for some live-attenuated formulations

A. Inactivated Vaccine (e.g., IXIARO®):

• Adults (≥18 years):
• 0.5 mL IM on Day 0 and Day 28
• Booster: 1 dose at 1 year if continued risk
• Children (2 months to <3 years):
• 0.25 mL IM on Day 0 and Day 28
• Children (≥3 years):
• 0.5 mL IM on Day 0 and Day 28

B. Live-Attenuated Vaccine (e.g., SA14-14-2):

• Children (9 months to 15 years):
• Single 0.5 mL dose SC
• Booster at 1 year (some countries recommend second dose)

Special Populations:

• Pregnant women: Generally contraindicated unless high risk; use only inactivated vaccine if benefit outweighs risk
• Immunocompromised patients: Live vaccines are contraindicated; inactivated vaccine preferred
• Elderly (≥65 years): Same dosing as adults, monitor for adverse events

The Encephalitis vaccine stimulates the host’s immune system to produce neutralizing antibodies against the Japanese Encephalitis Virus (JEV), a flavivirus transmitted by mosquitoes. Both live-attenuated and inactivated vaccines expose the immune system to viral antigens (mainly the envelope glycoproteins), which provoke a humoral immune response. This response leads to the generation of memory B cells and IgG antibodies, which remain circulating and neutralize the virus upon future exposure. Protective antibody levels are usually achieved within 10–14 days after the second dose (inactivated) or 28 days after a single dose (live).

As a vaccine, traditional pharmacokinetics (absorption, distribution, metabolism, excretion) do not apply in the same way as with drugs. However, immune response characteristics are as follows:

• Onset of Immunity:
• Inactivated vaccine: Protective immunity develops within 1–2 weeks after second dose
• Live vaccine: Protective immunity generally achieved within 28 days of a single dose
• Duration of Immunity:
• At least 1 year after full vaccination
• Some individuals retain protective antibodies for ≥5 years, but booster is advised if ongoing exposure risk
• Peak Antibody Titers:
• Achieved within 4–6 weeks post-vaccination
• No significant metabolism or systemic distribution occurs; immune activation is local and systemic via lymphatic response

• Pregnancy:
• Inactivated vaccine: Generally considered Category B (U.S.)
• May be administered during pregnancy if the risk of infection is high and benefits outweigh potential risks
• Live-attenuated vaccine: Contraindicated in pregnancy due to theoretical risk of fetal infection
• Lactation:
• Inactivated vaccine: Safe during breastfeeding; no excretion into breast milk or adverse infant effects reported
• Live vaccine: Use with caution; avoid unless benefits outweigh risks
• Recommendation: Avoid pregnancy for at least 28 days after receiving a live vaccine

• Primary Class: Vaccine (Active Immunizing Agent)
• Subclass: Antiviral vaccine – Japanese Encephalitis Virus (Flavivirus) Vaccine

• Known hypersensitivity to:
• Any component of the vaccine (e.g., gelatin, neomycin, formaldehyde)
• Previous dose of Japanese Encephalitis vaccine
• Severe allergic reaction (e.g., anaphylaxis) after any prior vaccine
• Live-attenuated vaccine only:
• Immunodeficiency (e.g., HIV/AIDS with low CD4 count)
• Pregnancy
• Infants <8 months of age
• Acute febrile illness (postpone vaccination until recovery)

• Allergic Reactions:
  Monitor for signs of anaphylaxis post-injection; emergency equipment should be available.
• Live Vaccine Risks:
• Contraindicated in immunocompromised individuals
• Avoid co-administration with other live vaccines unless clinically necessary
• Pregnancy & Breastfeeding:
• Use inactivated vaccine only if clearly indicated
• Avoid live vaccine during pregnancy
• Febrile Seizures:
• Rare reports after live-attenuated vaccine in children; observe closely post-vaccination
• Neurologic Events:
• Monitor for signs of encephalitis, Guillain-Barré syndrome, or hypersensitivity reactions post-vaccination (rare)

Common Side Effects (≥1%):

• Local (at injection site):
• Pain
• Redness
• Swelling
• Systemic:
• Fever
• Headache
• Fatigue
• Myalgia
• In Children (especially with live vaccine):
• Irritability
• Vomiting
• Diarrhea

Rare/Serious Adverse Effects:

• Anaphylaxis
• Febrile seizures
• Hypersensitivity reactions
• Neurologic symptoms (very rare):
• Encephalitis
• Guillain-Barré syndrome

Onset & Severity:

• Mild side effects occur within 1–3 days and resolve spontaneously
• Serious effects are extremely rare but require immediate medical evaluation

Drug–Vaccine Interactions:

• Immunosuppressive therapies (e.g., corticosteroids, chemotherapy):
• May reduce immune response to vaccine
• Live vaccine contraindicated during immunosuppressive therapy
• Other Vaccines:
• Live vaccine may be administered with other live vaccines (e.g., MMR, yellow fever) simultaneously or separated by at least 28 days
• Antiviral medications:
• No known interaction with JEV vaccines

Alcohol/Food Interactions:

• No known interactions
• Alcohol consumption does not interfere with vaccine efficacy

• WHO Position Paper (Latest):
• Recommends one dose of live-attenuated vaccine in children as part of routine immunization in endemic areas
• Endorses inactivated vaccine for travelers and lab personnel
• Travel Advisory Updates:
• CDC recommends vaccination for travelers visiting rural or agricultural areas of endemic countries, even for short durations if high mosquito exposure is anticipated
• Boosters:
• Newer guidance suggests one booster after 1 year may provide long-term protection (5+ years) in adults
• Combination Campaigns:
• Some Asian countries now integrate JE vaccination with other routine childhood immunizations

• Temperature:
  Store between 2°C and 8°C (36°F to 46°F)
  Do not freeze
• Humidity/Light Protection:
• Protect from direct sunlight
• Keep in original packaging until use
• Handling Precautions:
• Shake well before use (for suspension formulations)
• Discard if solution is discolored or contains particles
• Shelf Life:
  Use before the expiration date indicated on the vial or pre-filled syringe