Epidemic Meningitis

The goal of this clinical trial is to evaluate the immunogenicity and safety of an investigational group ACYW135 meningococcal conjugate vaccine in healthy children aged 2 to 6 years. 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, as measured by serum antibody levels? What safety profile does the investigational vaccine have in this pediatric population? Researchers will compare the investigational vaccine group with the control group (licensed ACYW135 polysaccharide vaccine) to determine if the new vaccine provides comparable immune protection with an acceptable safety profile. Participants will: Receive a single dose of either the investigational vaccine or the control vaccine by intramuscular injection; Provide two blood samples (before vaccination and 30 days after) for antibody testing; Have their vaccination site and overall health monitored for AE/AR immediately after injection, for 7 days and for 30 days through diary card and follow-up contacts; Be followed for serious adverse events for 6 months after vaccination. A total of 660 participants will be enrolled and randomly assigned in a 1:1 ratio to either the investigational group or the control group.

The goal of this clinical trial is to evaluate the immunogenicity, safety, and immune persistence of the primary series of an investigational group ACYW135 meningococcal conjugate vaccine, as well as the immunogenicity and safety of a booster dose administered at 12 months of age, in healthy children aged 3 to 5 months. The main questions it aims to answer are: Is the immune response induced by the primary series of the investigational vaccine non-inferior to that of the licensed control vaccine? What is the safety profile of the investigational vaccine during the primary series and booster dose? Does the investigational vaccine provide immune persistence up to 12 months of age? What is the immunogenicity of a booster dose administered at 12 months of age? Researchers will compare the investigational vaccine group with the active comparator group (CanSinoBIO MCV-ACYW) during both the primary immunization phase and the booster phase. Participants will: Be randomly assigned in a 1:1 ratio to receive either three doses of the investigational vaccine or three doses of the control vaccine according to a 0,1,2-month schedule during the primary immunization phase; Receive a booster dose at 12 months of age (either investigational vaccine or control vaccine according to group assignment); Provide blood samples at four time points: before primary vaccination, 30 days after primary vaccination, before booster vaccination (12 months of age), and 30 days after booster vaccination; 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 880 participants will be enrolled.

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.

The goal of this clinical trial is to evaluate the immunogenicity and safety of an investigational group ACYW135 Meningococcal conjugate vaccine in healthy children aged 12 to 23 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? What safety profile does the investigational vaccine have in this pediatric population? Researchers will compare the investigational vaccine group with the active comparator group (licensed ACYW135 meningococcal conjugate vaccine (CRM197 carrier), CanSinoBIO; hereinafter referred to as CanSinoBIO MCV-ACYW) to determine if the new vaccine provides comparable immune protection with an acceptable safety profile. Participants will: Receive two doses of either the investigational vaccine or the control vaccine according to a 0,1-month schedule; 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 completion of the primary immunization series; A total of 1040 participants will be enrolled and randomly assigned in a 1:1 ratio to either the investigational group or the control group.

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.