This clinical study will enroll 100 participants from the 2-month-old (minimum 6 weeks) group who previously participated in the Phase III clinical trial of the 13-valent pneumococcal polysaccharide conjugate vaccine (CRM197, TT vector) (Protocol No.: CS-CTP-PCV), with 50 participants in each of the treatment and control groups, and who have completed blood sample collection for the 1-year and 2-year immunogenicity studies. All participants will have 3.0-3.5 mL of venous blood collected for the immunogenicity study.

Inclusion Criteria:

• Participants in the 2-month-old (minimum 6 weeks) group from the previous Phase III clinical trial of the 13-valent pneumococcal polysaccharide conjugate vaccine (CRM197, TT vector) (Protocol No.: CS-CTP-PCV)
• The legal guardian or authorized representative is willing to provide identification documents
• The legal guardian or authorized representative has provided informed consent, voluntarily signed the informed consent form, and is able to comply with the requirements of the clinical study protocol
• The interval since the last dose of the primary vaccination series is ≥4 years

Exclusion Criteria:

• Failure to complete blood draws at 1 and 2 years post-vaccination
• Administration of any pneumonia vaccine after completion of the full vaccination series
• Body temperature ≥37.3°C
• Any other factors deemed by the investigator to render the participant unsuitable for participation in the clinical trial

This clinical study enrolled 100 participants from the 2-month-old (minimum 6 weeks) group who had previously participated in the Phase III clinical trial of the 13-valent pneumococcal polysaccharide conjugate vaccine (CRM197, TT vector) (Protocol No.: CS-CTP-PCV), with 50 participants in each of the treatment and control groups, and who had completed blood sample collection at 1 and 2 years post-vaccination to assess immunogenicity.