The study investigates a rapid immunization regime of the Japanese Encephalitis vaccine IC51 (JE-PIV) in healthy subjects aged > or = 18 years

This is a multicenter, observer blinded, controlled, randomized phase 3 study. The study population consists of healthy male and female volunteers, aged at least 18 years.

Approximately 375 volunteers will be enrolled at approximately 2 to 3 sites.

Inclusion Criteria:

• At least 18 years of age
• Written informed consent obtained prior to study entry

Exclusion Criteria:

• History of clinical manifestation of any flavivirus infection
• History of vaccination against Japanese encephalitis (JE), Yellow fever and Dengue fever (an anti-JEV neutralizing antibody titer >= 1:10 at baseline is acceptable for inclusion, these subjects will be part of the safety population, but will not be analyzed for immunogenicity in the per-protocol analysis)
• Use of any other investigational or non-registered drug or vaccine in addition to the study vaccine during the study period or within 30 days preceding the first dose of study vaccine
• Immunodeficiency including post-organ-transplantation or immunosuppressive therapy
• A family history of congenital or hereditary immunodeficiency
• History of autoimmune disease
• Any acute infections within 4 weeks prior to enrollment
• Infection with HIV, Hepatitis B or Hepatitis C
• Pregnancy, lactation or unreliable contraception in female subjects