This clinical trial is conducted in two parts. Part One employs a randomized, partially blinded, dose-escalation, partially active-controlled design. Part Two utilizes a randomized, blinded, placebo-controlled design. Part One is divided into four stages based on age and vaccine dose levels. Part Two consists of the 2-month-old vaccine/placebo groups.

Inclusion Criteria:

General Inclusion Criteria:

• Participants aged 2 months (60-89 days), 3 months (90-119 days), 18-24 months, and 6 years of age, with legal guardians or authorized representatives willing to provide identification documentation;
• Legal guardians or authorized representatives provide informed consent, voluntarily sign the informed consent form, and are able to comply with the requirements of the clinical trial protocol;

Part I: Specific Inclusion Criteria:

• Individuals aged 18-24 months who have completed a 3-dose DTaP-containing vaccine series and a meningococcal-containing vaccine primary series, but have not received a DTaP-containing booster dose;
• Individuals aged 6 years who have completed 4 doses of DTaP-containing vaccine but have not received the 5th DTaP-containing vaccine dose; and have only completed the first meningococcal-containing vaccine booster dose, without receiving the second meningococcal-containing vaccine booster dose at age 6.

Exclusion Criteria:

General Exclusion Criteria for First Dose：

• Infants born prematurely (delivery before 37 weeks gestation) or with low birth weight (<2500g) at 2 months (60-89 days) or 3 months (90-119 days) of age;
• Infants aged 2 months (60-89 days) or 3 months (90-119 days) with history of abnormal labor, asphyxia requiring resuscitation, or neurological impairment;
• Severe congenital malformations or developmental disorders, genetic defects, or severe malnutrition;
• History of severe adverse reactions or anaphylaxis to vaccines or vaccine components, such as urticaria, dyspnea, angioedema;
• History of epilepsy, convulsions, seizures, cerebral palsy, psychiatric disorders, or family history thereof; or history of progressive neurological diseases (e.g., Guillain-Barré syndrome, brachial plexus neuritis);
• Diagnosed with congenital or acquired immunodeficiency, HIV infection, lymphoma, leukemia, systemic lupus erythematosus (SLE), juvenile rheumatoid arthritis (JRA), or other autoimmune diseases;
• Acute illness (e.g., fever ≥38.5°C, diarrhea) or acute exacerbation of chronic disease within 3 days prior to receiving the investigational product;
• Known or suspected severe chronic diseases (including: severe respiratory disease, severe cardiovascular disease, liver/kidney disease, severe dermatology conditions, malignancies, etc.);
• Current anal abscess or severe eczema;
• Clinically diagnosed coagulation disorders (e.g., factor deficiency, bleeding disorders, platelet abnormalities) or significant bruising/coagulation impairment;
• Asplenia, functional asplenia, or splenectomy due to any cause;
• Continuous treatment with immunosuppressants, immunomodulators, or cytotoxic agents (exceeding 10 days) within the past 6 months; inhaled or topical steroids are permitted;
• Receipt of blood products or immunoglobulins (excluding hepatitis B immunoglobulin) within the past 3 months;
• Received an injectable live attenuated vaccine within 14 days, or any other vaccine within 7 days;
• Taken antipyretic analgesics or antiallergic medications within 3 days;
• Fever present prior to vaccination, with axillary temperature ≥37.3°C (99.3°F);
• Plans to participate in or is currently participating in any other drug/vaccine clinical trial;
• Any other factors deemed by the investigator to make the subject unsuitable for participation in the clinical trial.

Part I: Exclusion Criteria for the First Dose：

• Infants aged 2 months (60-89 days) who have received vaccines containing meningococcal, DTP, or Haemophilus influenzae type b components;
• Infants aged 3 months (90-119 days) who have received a vaccine containing meningococcal components;
• Individuals aged 18-24 months who have received vaccines containing meningococcal or Haemophilus influenzae type b components within the past six months;
• Individuals aged 18-24 months with abnormal pre-vaccination blood count or urinalysis results deemed clinically significant by the investigator;
• Children aged 6 years who, prior to vaccination, exhibit abnormal results in relevant indicators of complete blood count, blood biochemistry, coagulation function, or urinalysis, and are deemed clinically significant by the investigator;
• Individuals with a history of any of the following diseases: meningococcal meningitis, Haemophilus influenzae type b disease, pertussis, diphtheria, or tetanus.

Part II: Specific Exclusion Criteria for the First Dose

• History of vaccination with any meningococcal-containing vaccine;
• History of meningococcal disease. General Exclusion Criteria for Subsequent Doses：
• Occurrence of a serious adverse event related to vaccination following the previous dose;
• Vaccine-related Grade 3 or higher allergic reaction following the previous dose;
• Any other factors deemed by the investigator to make the subject unsuitable for continued participation in the clinical trial.

Part One: Partial Blind Method Design Part Two: Blind Method Design