Objective: To assess children initially vaccinated in 1992 with QMPV during a mass immunization against serogroup C meningococcal disease for total and functional antibody response a) 3 years post immunization and b) following a booster dose of vaccine. Subjects: Children initially vaccinated at 6-24 months of age with QMPV. Methods: Sera was measured by ELISA for total immunoglobulin A, G, and M response and by bactericidal assay (BA) for functional antibody response. Results: 133 subjects were assessed (Median age:4.3yrs; range 3.5-5.0yrs). GMC=Geometric mean concentration/GMT=Geometric mean titre. Vaccine Response {italics-primary response to QMPV of 3-5 year olds in 1992 study}.Table Implication: By 3 years post immunization a significant decline was seen in both functional and total antibody response thus children initially vaccinated less than 2 years of age may be unprotected in the event of a continued or new risk of serogroup C meningococcal disease. While the majority of children (>60%) responded to the booster immunization, in comparison to similar aged children vaccinated in the 1992 study, the booster response was associated with a higher GMC but a lower percentage achieving a minimal threshold response. (Funded in part by Connaught Lab; laboratory data by LCDC)

Table 1
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