Flavivirus Cross-priming Potential of IMOJEV

Inclusion Criteria: 1. A male or female adult between 18 and 70 years of age at consent. 2. Written and informed consent obtained from participant and agreement of participant to comply with the requirements of the study 3. Able to attend regularly to donate study blood samples for the duration of the study (8 weeks), no planned re-location or travel to a flavivirus endemic area during the study period. 4. Satisfactory medical screen, as demonstrated by study screening document normal physical examination and normal screening blood tests 5. Group 1: Any flavivirus exposure status; Group 2: No previous flavivirus vaccination (JE, tick borne encephalitis or yellow fever (YF)), no residence in a flavivirus endemic area nor planned travel to a flavivirus endemic area during the period of the study; Group 3: JE vaccine and/or yellow fever vaccine or other proven flavivirus infection within the last 10 years or other proven flavivirus infection (lifetime). 6. An efficacious method of contraception must be used during the study for women of childbearing potential. Exclusion Criteria: 1. Use of any investigational or non-registered drug within 5 half-lives of the drug, or 30 days preceding administration of study JE vaccine, whichever is longer; or planned use during the study period. 2. Receipt of any investigational biologic agents with mechanisms of action that might affect the immune system, at the discretion of the CI and local PI. 3. Administration of immunosuppressants or other immune-modifying drugs within a period of six months before vaccination or at any time during the study period; participants who have received these agents may also be excluded at the discretion of the CI and local PI. 4. Any confirmed or suspected immunosuppressive or immunodeficient condition. 5. A family history of congenital or hereditary immunodeficiency. 6. Any antiviral drug therapy within a period of 5 drug half-lives or 30 days before vaccination, whichever is longer, or at any time during the study period. 7. History of significant allergic reactions likely to be exacerbated by any component of the study vaccine, especially allergic disease or reactions to any previous dose of any vaccine. 8. History of having received JE vaccine, yellow fever vaccine, tick-borne encephalitis vaccine or experimental flavivirus vaccine (group 2 only). 9. Detectable anti Flavivirus neutralizing antibodies in screening tests (group 2 only). 10. Acute disease (for example acute infection) at the time of enrolment or vaccination, if symptoms are rated as anything more significant than a mild adverse event. Entry into the study and/or vaccination may be deferred until the illness has resolved for at least one week. 11. Acute or chronic, clinically significant in the opinion of the investigator, disease in any organ system, as determined by history, physical examination or laboratory testing. 12. Presence of any inflammatory condition that might require immunomodulatory therapy. 13. Recent blood donation (inclusion can be delayed under these circumstances; the participant should be enrolled 16 weeks after their last blood donation. Each participant should give no more than 470 ml per 16 weeks, so regular blood donation should be suspended during the study and can re-commence 1 month after the last study sample). 14. Current or previous abattoir worker or sheep farmer in Scotland (risk of Louping ill virus exposure; group 2 only). 15. Administration of immunoglobulins and/or any blood products within the three months preceding administration of vaccine, or planned administration during the study period. 16. Seropositive for HIV. 17. Pregnancy or Lactation. 18. History of excessive alcohol consumption (\>28 units per week), drug abuse or significant psychiatric illness. 19. Any other condition or consideration that, in the opinion of the Investigator, would pose a health risk to the participant if they were enrolled in the study, or would otherwise interfere with the evaluation of the study aims (e.g. difficult venesection).