A Phase Ib/II clinical trial of 24-valent pneumococcal conjugate vaccine (PCV24)developed by Sinovac Life Science Co., Ltd will be conducted in adults aged ≥18 years.

The objective of the study is to evaluate the safety and immunogenicity of Sinovac PCV24. The trial is a randomized, double-blind, Positive Controlled phase Ib/II clinical trial.

A phase Ib/II clinical trial of the study of 24-valent Pneumococcal Polysaccharide Conjugate Vaccine (PCV24) developed by Sinovac Life Science Co., Ltd (Sinovac) will be conducted in Chinese adults aged ≥18years.

The trial is a randomized, double-blind, positive controlled study. The objective of this study is to evaluate the safety and immunogenicity of PCV24 manufactured by Sinovac Life Science Co., Ltd. The active control vaccine is Pneumovax® manufactured by MSD.

Inclusion Criteria:

1. Healthy adults aged ≥18 years, who can provide legal identification documents
2. Fully understand and agree to sign the informed consent form
3. Willing and able to follow all study procedures and stay in contact during the study

Exclusion Criteria:

1. Received any pneumococcal vaccine;
2. History of invasive pneumococcal diseases or other pneumococcal diseases caused by Streptococcus pneumoniae, as confirmed by laboratory tests;
3. History of allergy or serious adverse reactions to the vaccine or vaccine components, or history of allergy, such as urticaria, dyspnea, angioedema and anaphylactic shock;
4. Congenital malformations or developmental disorders, genetic defects, severe malnutrition;
5. Have uncontrolled chronic diseases or history of severe diseases, including but not limited to cardiovascular diseases, metabolic diseases, hematological diseases,liver and kidney diseases, digestive diseases, respiratory diseases , malignant tumors and major functional organ transplantation history;
6. Autoimmune diseases or immunodeficiency diseases (including but not limited to systemic lupus erythematosus, rheumatoid arthritis,autoimmune thyroid disease, asplenia, functional asplenia, HIV infection);
7. Abnormalities in coagulation function (such as deficiency of coagulation factors, coagulation disorders, and abnormalities of platelets);
8. Have/have suffered from a serious neurological disorder (epilepsy , convulsions or seizures) or mental illness or have a family history of such diseases;
9. Long-term alcohol or drug abuse;
10. Have received > 14 days of immunosuppressive or other immunomodulatory therapy((such as prednisone ≥20 mg/day, or an equivalent dose)) in the past 6 months, or cytotoxic therapy, or plan to receive such therapy during the study period;
11. Received immunoglobulin or other blood products within 3 months before receiving the l vaccine, or plan to receive such treatment during the study period;
12. Received other investigational drugs or vaccines within 30 days before receiving the vaccine, or plan to receive such drugs or vaccines during the study;
13. Received live attenuated vaccine within 14 days before receiving the vaccine;
14. Received subunit or inactivated or other vaccine within 7 days before receiving the vaccine;
15. Acute diseases or acute onset of chronic diseases within the past 7 days , or known or suspected active infection;
16. Women who are breastfeeding or pregnant, or women of childbearing potential who plan to become pregnant or have egg donation plans from the time of signing the informed consent form until 6 months after the study intervention;
17. Participants who have a fever on the day of the planned trial vaccine, with an axillary temperature >37.0°C before vaccination;
18. Abnormalities in clinical laboratory indicators that exceed reference range and are clinically significant(Applicable only to phase Ib)
19. In the investigator's judgment, the participant has any other factors that make him or her unfit to participate in the clinical trial.