Dose-finding Study to Evaluate Immunogenicity of Three Different Dose Levels of the IMVAMUNE (MVA-BN) Smallpox Vaccine.

Inclusion Criteria: * Healthy male and female subjects, aged 18 - 30 years * Signed informed consent after being advised of the risks and benefits of the study in a language able to understand, and prior to performance of any study specific procedure. * Free of obvious health problems with acceptable medical history by screening evaluation and physical examination. * Subject of not of child-bearing potential or all of the following: A urine/serum ß-HCG pregnancy test gives a negative result, use of adequate contraceptive precautions for 30 days before first vaccination. Exclusion Criteria: * Known or suspected history of smallpox vaccination or typical vaccinia scar. * Positive test result in MVA specific ELISA or PRNT at screening. * Positive result in HIV or HCV antibody test at screening. * HbsAG positive at screening. * Pregnancy or breast-feeding. * Uncontrolled serious infection i.e. not responding to antimicrobial therapy * History of any serious medical condition, which in the opinion of the investigator, would compromise the safety of the subject. * History of autoimmune disease * History of malignancy. * History of chronic alcohol abuse and/or intravenous drug abuse. * History of allergic disease or reactions likely to be exacerbated by any component of the vaccine. * History of anaphylaxis or severe allergic reaction. * Acute disease (a moderate or severe illness with or without a fever) at the time of enrolment. * Any vaccinations within a period starting 30 days prior to administration of the vaccine and ending at study conclusion. * Chronic administration of immuno-suppressants or other immune-modifying drugs. * Administration or planned administration of immunoglobulins and/or any blood products during the study period. * Use of any investigational or non-registered drug or vaccine.