The goal of this clinical trial is to evaluate the immunogenicity, safety, and persistence of the immune response of a group ACYW135 meningococcal conjugate vaccine in healthy children aged 6 to 11 months.

The main questions it aims to answer are:

Is the immune response induced by the investigational vaccine non-inferior to that of the licensed control vaccine following the primary series? What is the safety profile of the investigational vaccine during the primary series and booster dose? Does the investigational vaccine provide durable immune persistence up to 18 months of age? What is the immunogenicity of a booster dose administered at 18 months of age? Researchers will compare the investigational vaccine group with the active comparator group (licensed group ACYW135 meningococcal conjugate vaccine (CRM197 carrier), CanSinoBIO) during the primary immunization phase. Only the investigational group will receive a booster dose at 18 months of age to evaluate booster immunogenicity and safety.

Participants will:

Be randomly assigned in a 1:1 ratio to receive either two doses of the investigational vaccine or two doses of the control vaccine according to a 0,1-month schedule during the primary immunization phase; In the investigational group only, receive a booster dose at 18 months of age; Provide blood samples at three time points: before primary vaccination, 30 days after primary vaccination, and at 18 months of age to assess primary immunogenicity and immune persistence; In the investigational group only, provide an additional blood sample 30 days after the booster dose to assess booster immunogenicity; Be observed for 30 minutes after each dose for immediate adverse reactions; Have solicited local and systemic adverse events recorded for 7 days after each dose using diary cards; Have unsolicited adverse events recorded for 30 days after each dose using diary cards; Be monitored for serious adverse events for at least 6 months after the last dose administered; A total of 1040 participants will be enrolled.

Inclusion Criteria:

1. Healthy participants aged 6 to 11 months.
2. The participant's legal guardian is capable of understanding and voluntarily signs the informed consent form.
3. Willing and able to comply with all scheduled visits, sample collection, vaccination, and other trial procedures.
4. Provision of legal identification documentation.

Exclusion Criteria:

1. History (or suspected history) of meningococcal disease.
2. History of infantile wheezing; history of allergy to the vaccine or any vaccine components (Group A/C/Y/W135 meningococcal capsular polysaccharide, mannitol, sucrose, sodium dihydrogen phosphate monohydrate, disodium hydrogen phosphate dodecahydrate, sodium chloride, water for injection), such as urticaria, dyspnea, angioedema; or other serious adverse reactions following prior vaccination.
3. Prior vaccination with any meningococcal vaccine (including but not limited to: Group A/C meningococcal polysaccharide/conjugate vaccine, ACYW135 meningococcal polysaccharide/conjugate vaccine, Group A meningococcal polysaccharide vaccine, etc.).
4. Presence of autoimmune diseases, immunodeficiency diseases (including but not limited to asplenia, functional asplenia, HIV infection in the participant or the participant's mother), or current perianal abscess.
5. Coagulation disorders (e.g., coagulation factor deficiency, platelet abnormalities) or history of significant bleeding, hematoma, or ecchymosis following intramuscular injection or venipuncture.
6. Presence of poorly controlled chronic diseases or history of serious illnesses, including but not limited to cardiovascular diseases, hematological diseases, hepatorenal diseases, gastrointestinal diseases, respiratory diseases, malignancies, or history of major organ transplantation.
7. Severe congenital anomalies, genetic defects, or malnutrition.
8. Presence of or history of severe neurological disorders [epilepsy, convulsions or seizures], or family history of psychiatric disorders.
9. Receipt of immunoglobulins or other blood products within the past 3 months, or planned receipt of such treatments during the study period.
10. Receipt of immunosuppressants or other immunomodulatory therapy for ≥14 days (e.g., prednisone ≥20 mg/day or ≥2 mg/kg/day, or equivalent), cytotoxic therapy within the past 6 months, or planned receipt of such therapies during the study period.
11. Receipt of any other investigational drug or vaccine within the past 3 months, or planned receipt during the study period.
12. Receipt of a live attenuated vaccine within the past 14 days, or receipt of a subunit or inactivated vaccine within the past 7 days.
13. Receipt of any other licensed vaccine within the past 28 days where administration at a different injection site from the study vaccine cannot be ensured.
14. Acute illness or acute exacerbation of chronic disease within the past 3 days, or known or suspected active infection.
15. Fever (axillary temperature >37.0°C) on the day of scheduled study vaccination, or abnormal findings on physical examination that preclude vaccination.
16. Skin lesions, inflammation, ulcers, rash, or scarring at the intended injection site that may interfere with vaccination or local reaction assessment.
17. Any other condition that, in the investigator's judgment, makes the participant unsuitable for participation in this clinical trial.