Phase II Clinical Trial of 24-valent Pneumococcal Polysaccharide Conjugate Vaccine

1. Volunteers aged 18 and above on the day of screening, and can provide legal identification;
2. Informed consent must be obtained from the volunteer and signed informed consent form;
3. Volunteers are able and willing to comply with the requirements of the clinical trial protocol and can attend all visits;
4. Armpit body temperature ≤ 37.0 °C on the day of enrollment.

5. Previous vaccination with pneumococcal conjugate vaccine, prior vaccination with pneumococcal polysaccharide vaccine for less than 3 years, or previous history of invasive disease caused by Streptococcus pneumoniae;
6. Have any history of severe allergies in the past, such as anaphylactic shock, allergic laryngeal edema, Henoch-Schonlein purpura, thrombocytopenic purpura, local allergic necrosis reaction (Athus reaction), etc.;
7. Have been diagnosed with congenital or acquired immunodeficiency, or have recently received immunosuppressant therapy, such as systemic glucocorticoid therapy such as prednisone or similar drugs >5 mg/day for more than 2 consecutive weeks in 1 month prior to vaccination);
8. Suffering from more serious cardiovascular diseases, such as arrhythmia, conduction block, myocardial infarction, severe hypertension that cannot be controlled by medication (systolic blood pressure ≥ 160 mmHg or diastolic blood pressure ≥100 mmHg when measured on site);
9. Those who have acute febrile illness or acute infectious disease or have cold symptoms, advanced influenza and take medication;
10. History of nervous system damage, severe congenital malformations, severe developmental disorders, severe genetic defects, severe malnutrition, etc.;
11. Have a history or family history of epilepsy, encephalopathy, or psychiatric disorders;
12. Those who have been diagnosed with thrombocytopenia, any abnormal coagulation function (such as coagulation factor deficiency, coagulation disorders, platelet abnormalities, etc.) or contraindications to intramuscular injection such as anticoagulant therapy;
13. asplenia, functional asplenia, and asplenia or splenectomy due to any cause;
14. Suffering from severe chronic diseases or the disease is in the advanced stage and cannot be controlled smoothly;
15. Have received blood or blood-related products or immunoglobulins within 3 months;
16. Received live attenuated vaccine within 14 days;
17. Other vaccinations within 7 days;
18. Received other investigational drugs or vaccines within 1 month;
19. Is participating in or plans to participate in clinical studies of other drugs or vaccines during the study period;
20. Any other condition that, in the opinion of the investigator, may interfere with the study evaluation;
21. Exclusion Criteria for Partial Populations:

Females of childbearing potential (18~49 years old): positive urine pregnancy test on the day of enrollment, lactation, or pregnancy plans within 6 months.