A Safety and Efficacy Study of Two Japanese Encephalitis Vaccines ChimeriVaxTM-JE and JE-VAX

• Number of Participants Who Seroconverted to the Respective Homologous JE Vaccine Strain Up to 28 Days After the First Active Vaccination With Either ChimeriVax™-JE or JE-VAX® Vaccine [ Time Frame: Day 0 (pre-vaccination) and up to Day 56 post-vaccination ] [ Designated as safety issue: No ]
  Immunogenicity was determined by analyzing antibody response of subjects to the respective homologous JE vaccine strain using a serum dilution 50% plaque reduction neutralization test (PRNT50). Seroconversion was defined as a 4 fold increase in antibody titer of ≥ 1:10 at baseline, or an antibody titer of ≥ 1:10 for participants with a baseline antibody titer of < 1:10.
• Mean Antibody Titers of the Respective Homologous JE Vaccine Strain After the First Active Vaccination With Either JE-Vax ® or ChimeriVax™-JE [ Time Frame: Day 0 up to Day 56 post-vaccination ] [ Designated as safety issue: No ]
  Immunogenicity was determined by analyzing antibody response of subjects to the respective homologous JE vaccine strain using a serum dilution 50% plaque reduction neutralization test (PRNT50).
• Number Participants That Were Seropositive to the Respective Homologous JE Vaccine Strain Before and Post-Vaccination With Either ChimeriVax™-JE or JE-VAX® Vaccine. [ Time Frame: Day 0 (Pre-vaccination) and up to Month 12 After First Dose ] [ Designated as safety issue: No ]
  Immunogenicity was determined by analyzing antibody response of subjects to the respective homologous JE vaccine strain using a serum dilution 50% plaque reduction neutralization test (PRNT50). Seropositive status for the ChimeriVax™-JE group was based on the ChimeriVax™-JE virus strain and positive status for the JE-VAX® group was based on the Nakayama virus strain. Participants were defined as seropositive if they had an antibody titer of ≥ 1:10. [Seropositive status can be 'Yes' or 'No']
• Mean Antibody Titers to the Respective Homologous JE Vaccine Strain Post Vaccination With Either ChimeriVax™-JE or JE-VAX® [ Time Frame: Day 0 (pre-vaccination) up to month 12 post-vaccination ] [ Designated as safety issue: No ]
  Immunogenicity was determined by analyzing antibody response of subjects to the respective homologous JE vaccine strain using a serum dilution 50% plaque reduction neutralization test (PRNT50).
• Number of Participants Reporting at Least One Treatment Emergent Adverse Event Following Vaccination With Either ChimeriVax™ JE or JE-VAX® [ Time Frame: Day 0 up to Day 6 post-vaccination ] [ Designated as safety issue: No ]
  Grade 3 (severe) adverse events were defined as incapacitating with inability to work or perform usual activity.

The purpose of this study is to determine non-inferiority in seroconversion and to compare the safety and tolerability between ChimeriVax™-JE and JE-VAX® to the respective homologous virus strain and several wild types strains after completion of vaccination course.

• Biological: ChimeriVax™-JE vaccine
  0.5 mL, subcutaneously
  Other Name: ChimeriVax™-JE
• Biological: JE-VAX® vaccine
  1.0 mL, subcutaneously
  Other Name: JE-VAX®

• Experimental: ChimeriVax™-JE
  Subjects received 2 injections of placebo (normal saline), 1 each on Days 0 and 7, and 1 injection of ChimeriVax™-JE on Day 28.
  Intervention: Biological: ChimeriVax™-JE vaccine
• Active Comparator: JE-VAX®
  Subjects received 1 injection of JE-VAX® each on Days 0, 7, and 28.
  Intervention: Biological: JE-VAX® vaccine

Inclusion Criteria:

• Written informed consent obtained.
• Aged ≥18 to <49 years.
• In good general health.
• Available for the study duration, including all planned follow-up visits.
• Females must have negative pregnancy test and be using adequate form of contraception

Exclusion Criteria:

• Clinically significant abnormalities on laboratory and vital sign assessments.
• Anaphylaxis or other serious adverse reactions
• Administration of another vaccine within 30 days of study treatment period.
• Physical examination indicating any significant medical condition.
• Intention to travel out of the area prior to the study visit on Day 56.
• Seropositive to Hepatitis C Virus (HCV) or Human Immunodeficiency Virus (HIV) or positive for Hepatitis B Surface Antigen.
• Pregnancy.
• Excessive alcohol consumption, drug abuse.
• Involvement in another clinical study within 60 days preceding the screening visit and during study treatment period.