The purpose of this study is to describe the immunogenicity and safety of IMOJEV® in adult and pediatric populations in Vietnam and serve a bridging study to compare immunogenicity, reactogenicity, and safety data obtained with IMOJEV® in the Vietnamese population with data from other Asian pediatric populations.

Primary objective:

- To describe the safety profile of a single dose of IMOJEV®.

Secondary objectives:

• To evaluate the immune response to JE 28 days after the administration of a single dose of IMOJEV® in healthy Vietnamese subjects aged from 9 months to 60 years.

Study participants will be enrolled by age group and will each receive one injection of IMOJEV® on Day 0 given as primary vaccination. They will be assessed for immunogenicity and safety, post-vaccination.

Inclusion Criteria:

• Aged 9 months through 60 years on the day of inclusion.
• For adults: Informed consent form has been signed and dated by the subject. For minors: Informed consent form has been signed and dated by the parent or legally acceptable representative. In addition, in accordance with the Institution Ethics Committee / Institution Review Board requirements and as appropriate for the age of the subject, the subject may be required to sign and date the informed consent form if aged 12 to 17 years or assent form if aged 8 to 11 years.
• Subject and parent(s)/legally acceptable representative(s) are able to attend all scheduled visits and comply with all study procedures.

Exclusion Criteria:

• Subject is pregnant, or lactating, or of childbearing potential (to be considered of non-childbearing potential, a female must be pre-menarche, or post-menopausal for at least 1 year, or surgically sterile, or using an effective method of contraception or abstinence from at least 4 weeks prior to vaccination until at least 4 weeks after vaccination).
• Participation at the time of study enrollment (or in the 4 weeks preceding the study vaccination) or planned participation during the present study period in another clinical study investigating a vaccine, drug, medical device, or a medical procedure.
• Receipt of any vaccine in the 4 weeks preceding the study vaccination or planned receipt of any vaccine in the 4 weeks following the study vaccination, except for inactivated influenza vaccination, which may be received at least 2 weeks before the study vaccine
• Previous vaccination against flavivirus disease, including Japanese Encephalitis (JE), dengue, and yellow fever.
• Receipt of immune globulins, blood, or blood-derived products in the past 3 months that might interfere with the assessment of the immune response.
• Known or suspected congenital or acquired immunodeficiency, or receipt of immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within the preceding 6 months, or long-term systemic corticosteroids therapy (for more than 2 consecutive weeks within the 4 weeks preceding vaccination).
• History of flavivirus infection (confirmed either clinically, serologically, or virologically).
• History of central nervous system disorder or disease, including seizures.
• Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccine used in the study or to a vaccine containing any of the same substances.
• Known thrombocytopenia, contraindicating vaccination.
• Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating vaccination.
• Deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized involuntarily.
• Current alcohol abuse or drug addiction.
• Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion.
• Febrile illness (temperature ≥ 38.0°C) or moderate or severe acute illness/infection on the day of vaccination, according to Investigator judgment. A prospective subject should not be included in the study until the condition has resolved or the febrile event has subsided.
• Receipt of any chronic anti-viral in the 2 months preceding the study vaccination or planned receipt of any anti-viral in the 4 weeks following the study vaccination. Short-term antiviral drugs for flu or herpes can be administered provided there is a wash-out period of 1 week before the administration of the vaccine.
• Identified as an Investigator or employee of the Investigator or study center with direct involvement in the proposed study, or identified as an immediate family member (i.e., parent, spouse, natural or adopted child) of the Investigator or employee with direct involvement in the proposed study.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org