Cut-off value was defined as 15 milli-international units per milliliter (mIU/mL). This was considered as seropositivity.

Cut-off values were defined 3.3 mIU/mL for the in-house anti-HBs assay and 6.2 mIU/mL for the ChemiLuminescence ImmunoAssay, which was also considered as seropositivity, and 10 mIU/mL.

Concentrations are expressed as geometric mean concentrations (GMCs) in mIU/mL. The laboratory assay was changed from Year 13 to Year 14 to in-house ELISA and at Year 15 to CLIA for anti-HBs GMCs.Thus for the sake of bridging, blood samples corresponding to Year 14 previously tested with ELISA were re-tested with CLIA (Year 14\*).

Subjects who lost seroprotective concentrations for anti-HBs (\< 10 mIU/mL) at any of the LT follow-up timepoints received an additional dose of Engerix after year 15. Two subjects were eligible for this after Year 11. 3.29 in the table means a concentration of \< 3.3 mIU/mL. As the concentration was calculated per subject no mean concentration was calculated and also no measure of dispersion.

Anamnestic response was assessed in subjects receiving an additional vaccine dose of Engerix. Two subjects were found eligible at Year 11 for this additional vaccine dose. Anamnestic response was defined as: * post-additional vaccination anti-HBs concentration \>= 10 mIU/mL in subject seronegative before additional dose. * 4-fold increase post-additional dose compared to pre-additional vaccine time point.

Solicited local symptoms were pain, redness and swelling. Solicited general symptoms were fatigue, fever, gastrointestinal, headache.

Unsolicited AE covers any AE reported in addition to those solicited during the clinical study and any solicited symptom with onset outside the specified period of follow-up for solicited symptoms.

SAEs assessed include medical occurrences that result in death, are life threatening, require hospitalization or prolongation of hospitalization, result in disability/incapacity or are a congenital anomaly/birth defect in the offspring of a study subject

SAEs assessed include medical occurrences that result in death, are life threatening, require hospitalization or prolongation of hospitalization, result in disability/incapacity or are a congenital anomaly/birth defect in the offspring of a study subject.