Immune Responses After a Booster Immunisation With IXIARO® in Elderly Compared to Young Individuals.

Inclusion Criteria: * participation in the preceeding study "IXIARO®-senescence" (EudraCTno: 2010-018630-52) without protocoll violation OR 2 documented IXIARO® vaccinations 28 days (-8/+ 30 days) apart between January 2010 and April 2014 at the age of 18 to 40 years or above the age of 60. * good state of health including individuals with medically controlled minor underlying disease (such as hypertension, hypercholesterinemia, NIDDM) * willingness to sign written informed consent major Exclusion Criteria: * Already received an booster (3rd dose) of IXIARO ® * Vaccination with other JE vaccine (e.g. Je-vax) * clinically manifest infection with another Flavivirus within 1 year prior study inclusion (yellow fever, Dengue fever, West Nile, TBE) * past infection with the JEV * vaccination against yellow fever, Dengue, West Nile within 6 months prior to study inclusion * TBE vaccination within the last 30 days prior to study inclusion * immunosuppressive therapy (intake\>14d) within 30 days before IXIARO booster till V3 (day 42+/-4), Corticosteroids like Prednisolon \> and = 20mg/day; allowed: topic or inhalative application * immunodeficiency or st. p. organ transplantation * autoimmune disease except vitiligo or diseases of the thyroid gland with thyroid hormon substitution therapy * immuntherapy within 2 weeks before or after Ixiaro Booster * current acute infection or exacerbation of a chronic illness * cancer within the last 5 years * clinically significant haematological, renal, pulmonary, hepatic, neurological, cardiovascular disease which is not treated adequately within 12 weeks before Ixiaro booster * known infection with HIV, Hep B and Hep C * Guillain - Barré- Syndrome (GBS) - anamnestic * anamnestic anaphylaxie, atopy oder severe hypersensivity against ingredients of IXIARO * drug abuse/alcohol abuse * pregnancy and breastfeeding * plasma donation within the last 4 months * receiving blood or immunglobulins within 3 months before v1 * significant mental disorder