<qa>  What is the long-term follow-up study at Years 11, 12, 13, 14, 15, 16, 17,This is a long-term follow-up study at Years 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 after primary vaccination with GSK Biologicals hepatitis A vaccine two-dose schedule. To evaluate the long-term antibody persistence, volunteers will donate a blood sample at Years 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 after the first vaccine dose of the primary vaccination course to determine their anti-hepatitis A anti-HAV antibody concentrations. 