A Prospective, Open Label Study of Human T Cell Responses to Live Attenuated Japanese Encephalitis Vaccine SA14-14-2

Inclusion criteria: * A male or female adult between 18 and 50 years of age. * Written informed consent. * Free of obvious health problems as established by medical history and history- directed physical examination before entering the study. * Expected continuous residence in India during study period, without travel outside India * An efficacious method of contraception must be used during the study for women of childbearing potential. Exclusion Criteria: * Use of any investigational or non-registered drug or vaccine other than the study vaccine within 30 days preceding administration of SA14-14-2 vaccine, or planned use during the study period. * Chronic administration of immunosuppressants or other immune-modifying drugs within a period of six months before vaccination or at any time during the study period. * Any confirmed or suspected immunosuppressive or immunodeficient condition. * A family history of congenital or hereditary immunodeficiency. * Any antiviral drug therapy within a period of six months before vaccination or at any time during the study period. * History of significant allergic disease or reactions likely to be exacerbated by any component of the study vaccine, especially allergic disease or reactions to any previous dose of any vaccine. * History of having received JE vaccine, yellow fever vaccine, tick-borne encephalitis vaccine or experimental flavivirus vaccine. * History of documented JE infection. * Detectable anti JE or West Nile neutralizing antibodies in screening tests. * Acute disease at the time of enrollment. Entry into the study may be deferred until the illness is resolved. * Acute or chronic, clinically significant, pulmonary, cardiovascular, hepatic, neurological or renal functional abnormality, as determined by history and physical or laboratory examination that is not controlled by drugs. * Administration of immunoglobulins and/or any blood products within the three months preceding administration of vaccine, or planned administration during the study period. * Seropositive for HIV, HCV or HbsAg. * Lactation, pregnancy or intention to get pregnant. * History of excessive alcohol consumption, drug abuse or significant psychiatric illness. * Any other condition that in the opinion of the investigator would pose a health risk to the participant or interfere with the evaluation of the vaccine.