Boosterability of Live Attenuated Japanese Encephalitis (JE) Vaccine in Children Who Have Previously Received Inactivated JE Vaccine

Inclusion Criteria:

• Healthy child 2 years (±3 months) or 5 years (±3 months) of age at the enrollment visit.
• Subject was a full-term infant.
• Subject's parent or legal guardian is literate and willing to provide written informed consent.
• Subject is up-to-date for all vaccinations recommended in the Sri Lankan childhood immunization schedule.

Exclusion Criteria:

• Enrolled in another clinical trial involving any therapy.
• Subject and/or parent(s) or guardian(s) are unable to attend the scheduled visits or comply with the study procedures.
• Received any non-study vaccine within 2 weeks prior to enrolment or refusal to postpone receipt of such vaccines until 28 days after study entry.
• Prior or anticipated receipt of immune globulin or other blood products, or injected or oral corticosteroids or other immune modulator therapy except routine vaccines within 6 weeks of administration of study vaccine. Individuals on a tapering dose schedule of oral steroids lasting <7 days may be included in the trial as long as they have not received more than one course within the last 2 weeks prior to enrolment.
• History of documented or suspected encephalitis, encephalopathy, or meningitis.
• History of measles.
• History of Japanese encephalitis.
• Serious adverse event related (i.e., possible, probably, definite) to previous receipt of any JE vaccine, if applicable.
• Persistent inconsolable crying (>3 hours) observed after previous receipt of any JE vaccine, if applicable.
• Hypotonic - hyporesponsiveness after past receipt of any JE vaccine, if applicable.
• Suspected or known hypersensitivity to any of the investigational or marketed vaccine components.
• History of serious chronic disease (cardiac, renal, neurologic, metabolic, or rheumatologic).
• Underlying medical condition such as inborn errors of metabolism, failure to thrive, bronchopulmonary dysplasia, or any major congenital abnormalities requiring surgery or chronic treatment.
• History of thrombocytopenic purpura.
• History of seizures, including history of febrile seizures, or any other neurologic disorder.
• Known or suspected immunologic function impairment of any kind and/or known HIV infection.
• Parent with known or suspected immunologic function impairment of any kind and/or known HIV infection.
• Any condition that, in the opinion of the investigator, would pose a health risk to the participant or interfere with the evaluation of the study objectives.