Follow-up Study on the Antibody Response to Hepatitis B, Acellular Pertussis Toxin and Inactivated Poliovirus Antigens 1 Month After the 4th Hexavac® Vaccination in Healthy Children, Who Participated in NeisVac-C Study 216

Inclusion Criteria: Study subjects who completed study 216 will be eligible for participation in this study if: * they received all 3 vaccinations with Hexavac during study 216 and the 4th Hexavac vaccination outside the study * the subject's parent(s)/legal guardian(s) understands the study and has provided written informed consent for his/her child's study participation; * a blood draw was performed after the 3rd vaccination during study 216. Exclusion Criteria: Study subjects will be excluded from participation in this study if: * they have received any vaccination containing hepatitis B, poliovirus or acellular pertussis toxin antigens other than Hexavac * they have received a blood transfusion or immunoglobulins during the period from 28 days prior to the 4th Hexavac vaccination until study entry * they have received another vaccine during the period from 28 days prior to the 4th Hexavac vaccination until study entry * they are concurrently participating in or have participated in a clinical trial with an investigational medicinal product since the completion of study 216 * they suffer from a disease (e.g. autoimmune disease) or were undergoing a form of treatment that may be expected to influence immunological functions since the completion of study 216 * they have received systemic corticosteroids during the period from 28 days prior to the 4th Hexavac vaccination until study entry.