1) To study the long-term immune response between the two groups 3-5 years after vaccination with PCV13 or PPSV23, measured as the proportion of subjects with a positive vaccination response in each of the two groups. 2) To study the short-term immune response 8 weeks and 16 weeks after revaccination of the initial PCV 13 Group A with PCV13/PPSV23 and of the initial PPSV23 Group B with PCV13/PCV13, measured as the proportion of subjects with a positive vaccination response pre- and post- revaccination.

1) To study the long-term immune response between the two groups 3-5 years after vaccination with PCV13 or PPSV23, measured as the proportion of subjects with a positive vaccination response in each of the two groups. 2) To study the short-term immune response 8 weeks and 16 weeks after revaccination of the initial PCV 13 Group A with PCV13/PPSV23 and of the initial PPSV23 Group B with PCV13/PCV13, measured as the proportion of subjects with a positive vaccination response pre- and post- revaccination.