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.
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;
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.
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;
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Treatment groupsSee each treatment group below.