[Study on the safety and immunogenicity of ACYW135 meningococcal polysaccharide conjugate vaccine in children aged 4-6 years].

Objective: To evaluate the safety and immunogenicity of ACYW135 meningococcal polysaccharide conjugate vaccine (MPCV4) in 4-6 years old children. Methods: A randomized, blinded, and controlled study of similar vaccines was conducted from September to November 2023. Subjects aged 4-6 years who had completed at least doses of the primary immunization with meningococcal polysaccharide vaccines according to the immunization program were recruited in Shanyang County and Linwei District of Shaanxi Province. They were randomly assigned to the experimental group and the control group at a 1∶1 ratio and were vaccinated with the experimental vaccine MPCV4 or the already marketed meningococcal polysaccharide vaccine against serogroups A, C, Y, and W135 (control vaccine), respectively. Adverse reactions occurred within 0-30 days after vaccination, and serious adverse events (SAEs) were observed within 180 days after vaccination. Serum samples were collected before immunization and 30 days after immunization to detect the bactericidal antibodies against Neisseria meningitidis of serogroups A, C, Y, and W135. The incidence of adverse reactions, GMT of antibodies, seroconversion rate, and positivity rate were analyzed. Results: For immunogenicity analysis, 462 participants were enrolled in the experimental group and 466 in the control group, the seroconversion rates of group A antibodies after immunization were 98.05% and 94.21% respectively (P=0.002), and the GMTs were 458.89 and 123.14 respectively (P<0.001); the seroconversion rates of group C antibodies were 78.57% and 60.09% respectively (P<0.001), and the GMTs were 78.96 and 17.49 respectively (P<0.001); the seroconversion rates of group Y antibodies were 78.35% and 47.00% respectively (P<0.001), and the GMTs were 118.93 and 14.29 respectively (P<0.001); the seroconversion rates of group W135 antibodies were 87.88% and 58.80% respectively (P<0.001), and the GMTs were 142.82 and 11.53 respectively (P<0.001). The total incidence rates of adverse reactions within 0-30 d after immunization in the experimental and control groups were 35.76% and 32.19% respectively (P=0.236), among which the incidences of local adverse reactions were 12.93% and 13.68% respectively (P=0.727), and the incidences of systemic adverse reactions were 24.44% and 20.93% respectively (P=0.186). Conclusion: The MPCV4 used in this study showed good safety and immunogenicity in 4-6 years old children.