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

The aim of this study is to investigate the immune responses following a booster immunisation with the Japanese Encephalitis vaccine in elderly subjects (above 60 years of age) in comparison to a young study group.

The condition under investigation is the naturally aging immune system. The aim of this study is to investigate the immune responses following a booster immunisation with the Japanese Encephalitis vaccine in elderly subjects (above 60 years of age) in comparison to a young study group.Testing the difference of the JEV-antibody titre increase between young and elderly adults between visit 1 (before booster vaccination) and up to visit 4 (6 months after booster vaccination).

Testing cellular immunity (cytokine production after JEV as well as TBE stimulation) on visit 1, 2 (one week after booster immunisation) and 3 between both age groups.

Testing of surface markers of different T and B cell subsets before and after JE-booster vaccination (on visit 1-3) in comparison between both age groups.

Testing TBE-antibody titres before and after JE-booster vaccination (on visit 1-4) in both age groups.

Testing CMV serology at visit 1 in both age groups.

Eligibility Criteria:
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