A phase 1b clinical trial of 13-valent Pneumococcal Polysaccharide Conjugate Vaccine (PCV13) developed by Sinovac Life Science Co., Ltd will be conducted in children aged 2 months (42-89 days) and 2 to 5 years. The objective of the study is to evaluate the safety and immunogenicity of Sinovac PCV13. The trial is a randomized, double blinded, positive controlled study.

A phase Ⅰb clinical trial of the study of 13-valent Pneumococcal Polysaccharide Conjugate Vaccine (PCV13) developed by Sinovac Life Science Co., Ltd (Sinovac) will be conducted in Chinese children aged 2 months (42-89 days) and 2 to 5 years. The trial is an randomized, double-blind and active controlled study. The objective of this study is to evaluate the safety and immunogenicity of PCV13 manufactured by Sinovac Life Science Co., Ltd. The active control vaccine is the PREVNAR 13 manufactured by Pfizer Inc. A total of 140 participants will be enrolled, including 70 children aged 2-5 years old, and 70 infants aged 2 months (42-89 days). Participants will be randomized to receive either Sinovac PCV13 or Pfizer PCV13 in a 1:1 ratio. Children aged 2-5 years old will receive 1 dose; Infants aged 2 months will receive 4 doses, including 3 doses (two-month interval) in primary vaccination and a booster dose at the age of 12-15 months.

Inclusion Criteria:

1. Healthy infants aged 2 months (42-89 days); Healthy children aged 2-5 years.
2. Proven vaccination certificate, birth certificate and legal identification documents
3. The participants' guardians can understand and voluntarily sign the informed consent form.
4. Participants and their guardians can obey requirements of the protocol.

Exclusion Criteria:

1. Received any pneumococcal vaccine prior to enrollment.
2. History of culture confirmed bacterial pneumonia or invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae.
3. History of allergy to the vaccine or vaccine components, including pneumococcal polysaccharide for each serotype, diphtheria CRM197, aluminum phosphate, succinic acid, polysorbate 80 and sodium chloride; or serious adverse reactions to the vaccine, such as urticaria, dyspnea, angioedema and asthma.
4. History of dystocia, asphyxia rescue, nervous system damage at birth (only applicable to infants aged 2 months (42-89 days))
5. Congenital malformations or developmental disorders, genetic defects, severe malnutrition, asthma etc.
6. Autoimmune disease (such as systemic lupus erythematosus) or immunodeficiency/ immunosuppression (such as HIV, organ transplantation)
7. Severe cardiovascular diseases, such as diabetes, liver diseases, kidney diseases, malignant tumors.
8. Family history of mental illness, severe neurological disease (epilepsy or convulsions) or mental illness.
9. History of thyroidectomy, asplenia, functional asplenia; and asplenia or splenectomy resulting from any condition.
10. Diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy, abnormal platelets), history of obvious bleeding or bruising after intramuscular injection or venipuncture.
11. Infants 2 months of age (42-89 days) prior to enrollment/children 2 to 5 years of age 6 months prior to enrollment had been treated with corticosteroids, other immunosuppressive agents (excluding corticosteroid spray therapy for allergic rhinitis, superficial corticosteroid therapy for acute non-concurrent dermatitis) or cytotoxic therapy for ≥14 days
12. Infants 2 months of age (42-89 days) prior to enrollment/children 2 to 5 years of age 3 months prior to enrollment received blood products within the past 3 months (excluding hepatitis B immunoglobulin within 1 month).
13. Receipt of other investigational drugs in the past 60 days or have the plan to participate in other clinical trials during this study.
14. Receipt of attenuated live vaccines in the past 14 days.
15. Receipt of inactivated or subunit vaccines in the past 7 days.
16. Acute diseases or acute exacerbation of chronic diseases in the past 7 days.
17. Axillary temperature ≥37.3 °C.
18. According to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.