Primary Objective:

To describe the persistence of Hep B antibodies (Ab) at 12 to 18 months of age following a three-dose infant primary series vaccination of either Hexaxim®/Hexyon®/Hexacima® or Infanrix® hexa at 2, 4 and 6 months of age following Hep B vaccination at birth.

Sera from subjects who have participated in study PNA19 trial (NCT00594347) and for whom parents or legal representatives had given authorization to use the sera taken from their child will be used for this study.

Inclusion Criteria:

• Subjects having received 4 Hep B doses in A3L12 (i.e. one dose at birth + three doses during study at 2, 4 & 6 months of age)
• Subjects having participated in PNA19
• Subject's parents having given authorization to use serum collected in PNA19 for future research
• The initials, birth date, and gender of the subject are consistent between A3L12 and PNA19 databases
• Subjects for whom retention sera are of enough volume to allow a valid determination of the HBsAg antibody level.

Exclusion Criteria:

• Not applicable.