The impact of vaccination with MCC vaccine on the prevalence of carriage of group C meningococci was consistent with herd immunity. The high impact on the carriage of ST-11 complex serogroup C could be attributed to high levels of capsule expression. High vaccine efficacy against disease in young children, who were not protected long-term by the schedule initially used, is attributed to the high vaccine efficacy against carriage in older age groups.

Background. Herd immunity is important in the effectiveness of conjugate polysaccharide vaccines against encapsulated bacteria. A large multicenter study investigated the effect of meningococcal serogroup C conjugate vaccine introduction on the meningococcal population.Methods. Carried meningococci in individuals aged 15–19 years attending education establishments were investigated before and for 2 years after vaccine introduction. Isolates were characterized by multilocus sequence typing, serogroup, and capsular region genotype and changes in phenotypes and genotypes assessed.Results. A total of 8462 meningococci were isolated from 47 765 participants (17.7%). Serogroup prevalence was similar over the 3 years, except for decreases of 80% for serogroup C and 40% for serogroup 29E. Clonal complexes were associated with particular serogroups and their relative proportions fluctuated, with 12 statistically significant changes (6 up, 6 down). The reduction of ST-11 complex serogroup C meningococci was probably due to vaccine introduction. Reasons for a decrease in serogroup 29E ST-254 meningococci (from 1.8% to 0.7%) and an increase in serogroup B ST-213 complex meningococci (from 6.7% to 10.6%) were less clear.Conclusions. Natural fluctuations in carried meningococcal genotypes and phenotypes a can be affected by the use of conjugate vaccines, and not all of these changes are anticipatable in advance of vaccine introduction.

BackgroundMeningococcal carriage studies are important to improve our understanding of the epidemiology of meningococcal disease. The aim of this study was to determine the prevalence of meningococcal carriage and the phenotypic and genotypic characteristics of isolates collected from a sample of students in the city of Bogotá, Colombia.Materials and MethodsA total of 1459 oropharyngeal samples were collected from students aged 15–21 years attending secondary schools and universities. Swabs were plated on a Thayer Martin agar and N. meningitidis was identified by standard microbiology methods and PCR.ResultsThe overall carriage prevalence was 6.85%. Carriage was associated with cohabitation with smokers, and oral sex practices. Non-groupable and serogroup Y isolates were the most common capsule types found. Isolates presented a high genetic diversity, and circulation of the hypervirulent clonal complexes ST-23, ST-32 and ST-41/44 were detected.ConclusionThe meningococcal carriage rate was lower than those reported in Europe and Africa, but higher than in other Latin American countries. Our data also revealed antigenic and genetic diversity of the isolates and the circulation of strains belonging to clonal complexes commonly associated with meningococcal disease.

In 2011, Chile experienced an increase in the number of cases of IMD caused by Neisseria meningitidis group W. This epidemiological scenario prompted authorities to implement prevention strategies. As part of these strategies, the Institute of Public Heath of Chile conducted a cross-sectional study to determine the prevalence of pharyngeal carriage of N. meningitidis in a representative sample of healthy children and adolescents aged 10-19 years. The identification of presumptive N. meningitidis strains was performed by testing carbohydrate utilization in the National Reference Laboratory at the ISP. Association of meningococcal carriage with risk factors was analyzed by calculating the Odds Ratio. Selected variables were included in a logistic model for risk analyses. The prevalence of carriage of N. meningitidis was 6.5% (CI: 5.7-7.3%). Older age (carriers: 14.2±0.29 vs. non-carriers: 13.8±0.08 years old; p=0.009), cohabitation with children (carriers: 0.9±0.13 vs. non-carriers: 0.7±0.03; p=0.028), number of smoking cohabitants (carriers: 0.55±0.13 vs. non-carriers: 0.44±0.03) and frequent attendance to crowded social venues (carriers: 49% vs. non-carriers: 37%; p=0.008) were determined to favor carriage. Statistical modeling showed that meningococcal carriage was associated with older age (OR: 1.077, p-value: 0.002) and cohabitation with children (OR: 1.182, p-value: 0.02).