 This study will evaluate the persistence of the immune response to HAV hepatitis A virus antigens and HBs hepatitis B surface antigens in healthy adults previously vaccinated with TwinrixTM Adult in the primary study, HAB-032 208127022. The subjects will be invited for blood sampling 16, 17, 18, 19 and 20 years after the primary vaccination to evaluate the antibody persistence. For subjects in whom low circulating antibodies are detected, the presence of immune memory against hepatitis A B antigens will be investigated by the administration of a challenge dose of the appropriate vaccine HavrixTM andor EngerixTM-B at the next planned visit. 