Tick-Borne Encephalitis (TBE) Seropersistence After First Booster and Response to a Second Booster in Children, Adolescents and Young Adults (Follow-Up to Study 700401)

Inclusion Criteria: Subjects who participated in precursor Study 700401 and meet ALL of the following criteria are eligible for participation in this study: * Subject / parent(s) / legal guardian(s) provide(s) written informed consent (according to national law); * Subject provides written assent to the study according to age and capacity of understanding; * Subject received the first booster vaccination with either FSME-IMMUN 0.25 ml Junior or FSME-IMMUN 0.5 ml during the course of precursor Study 700401; * Blood was drawn after the first booster vaccination in precursor Study 700401; * Subject / parent(s) / legal guardian(s) understand(s) the nature of the study and is / are willing to comply with the requirements of the protocol (e.g. return for follow-up visits, completion of the Subject Diary). Exclusion Criteria: Subjects who participated in precursor Study 700401 and meet ANY of the following criteria are not eligible for participation in this study: * Subject received any TBE vaccination since his / her first booster vaccination in precursor Study 700401; * Subject has a history of infection with or vaccination against other flaviviruses (e.g. Dengue fever, yellow fever, Japanese B encephalitis) since his / her first booster vaccination in precursor Study 700401; * Subject is known to be HIV positive since his / her first booster vaccination in precursor Study 700401 (a special HIV test is not required for the purpose of the study); * Subject received a blood pro…