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.