Japanese encephalitis (JE) live attenuated vaccine SA14-14-2 has been in use for more more than 20 years in Asia. JE vaccine SA14-14-2 is licensed in India and has been widely used since 2006. JE vaccines give protection by generating a neutralizing antibody response, but both naturally exposed persons and patients with JE also have T cell responses. Whether JE vaccine SA14-14-2 elicits T cell responses is unknown. This study tests the hypothesis that T cell responses are generated in response to JE SA14-14-2 vaccination. The aim of this study is to characterize T cell responses to JE vaccine SA14-14-2 in healthy people, and to investigate differences in T cell responses between natural exposure, vaccination and disease.

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.