Inclusion Criteria  Elderly people aged 70-75 years Had received PPSV23 in the previous 5-7 years  Exclusion Criteria:  Immunocompromised patients Subjects receiving immunosuppressive agents Subjects with a history of vaccination with pneumococcal conjugate vaccine Subjects with a history of pneumococcal disease (positive culture from blood or other sterile fluid) Fever (defined as an oral temperature >37.5℃) within 24 h before PPSV23 vaccination