This study included 180 trial participants who had previously taken part in the Phase IIIb clinical trial of the ACYW135 group meningococcal polysaccharide-conjugated vaccine (CRM197 carrier) for children aged 4-6 years (Protocol No.: CTP-MCVF-002) and had completed blood sample collection at 90 and 180 days post-vaccination; there were 90 participants in each of the treatment and control groups. All trial participants were required to provide 3.0-4.0 mL of blood samples for immunopersistence assessment at 3 and 5 years post-vaccination, respectively.