Age-related immunogenicity of meningococcal polysaccharide vaccine in aboriginal children and adolescents living in a Northern Manitoba reserve community

Objective. To determine the total and functional serogroup C antibody response to a quadrivalent meningococcal polysaccharide vaccine in a group of aboriginal infants, children and adolescents. A secondary objective was to determine their prevalence of meningococcal carriage. Design. Open prospective, before and after intervention study. Subjects. Aboriginal children ages 0.5 to 19.9 years, living in a single Northern community and eligible for a public health immunization campaign conducted in all Manitoba native reserve communities to control a meningococcal sero-group C, electrophoretic type (ET) 15 outbreak. No outbreak cases had occurred in the community at the time of the study. Methods. Total serogroup C capsular polysaccharide antibody CPA and functional bactericidal antibody (BA) responses were measured by enzyme-linked immunosorbent assay and bactericidal assay, respectively. Results. Neisseria meningitidis was recovered from the oropharynx of 13 (5.2%) of 249 aboriginal children including 4 (1.6%) serogroup C isolates, all with the designation C:2a:P1.2,5 ET15. Paired sera from 152 children were available for assay. For CPA the geometric mean concentrations and proportions with ≥2 μg/ml before and after immunization were 0.69, 18% and 12.3, 96%, respectively. A significant increase in serum CPA was achieved by children of all ages, with the greatest response occurring after age 11 years. Among infants <1year old 89% achieved concentrations of ≥2 μg/ml. For BA the pre- and post-vaccine geometric mean titers were 1.02 and 45.9. The response was significantly associated with age. BA titers ≥1:8 were present, before and after immunization, respectively, in 0 and 0% of infants <1 year old, 0 and 20% of 1- to 1.4- year-olds, 0 and 50% of 1.5- to 1.9-year-olds and 1 and 100% of ≥2-year- olds. Conclusion. The age-related total and functional group C meningococcal antibody response after quadrivalent polysaccharide vaccine among aboriginals is similar to that reported for Caucasian children. After age 2 all children made excellent CPA and BA responses. In the younger age groups the BA response was blunted but 82 to 95% achieved CPA titers of ≥2 μg/ml.