Meningococcal Carriage among Adolescents after Mass Meningococcal C Conjugate Vaccination Campaigns in Salvador, Brazil

Neisseria meningitidis is a commensal bacterium of the human nasopharynx. In rare cases, it penetrates the mucosa, entering the blood stream and causing various forms of disease. Meningococcal conjugate vaccines can prevent invasive disease not only by direct effect in vaccinated individuals but also by herd protection, preventing acquisition of carriage, which interrupts transmission and leads to protection of unvaccinated persons. In 2010 in Salvador, Brazil, an outbreak of group C meningococcal disease led to a mass meningococcal serogroup C conjugate vaccination drive, targeting those <5 and 10-24 years of age. The present study aimed to estimate the prevalence of and identify factors associated with N. meningitidis carriage among adolescents from Salvador, Brazil, in the post-vaccination period. In spring 2014, we performed a cross-sectional study involving 1,200 public school students aged 11-19 years old. Oropharyngeal swabs were collected to identify N. meningitidis. Of the 59 colonized participants, 36 (61.0%) carried non-groupable N. meningitidis, while genogroup B (11.9%), Y (8.5%), E (6.8%), Z (5.1%), C (3.4%), and W(3.4%) were also detected. The overall prevalence of N. meningitidis carriage was 4.9% (95% confidence interval [CI], 3.6-6.1%); the prevalence of N. meningitidis genogroup C was 0.17% (95% CI, 0.0-0.40%). There was no difference by age. Factors associated with carriage were having only one, shared, bedroom in the household (PR, 2.02; 95% CI, 0.99-4.12, p = 0.05); the mother being the only smoker in the home (PR, 2.48; 95% CI, 1.16-5.29; p = 0.01); and going to pubs/parties more than 5 times/month (PR, 2.61; 95% CI, 1.38-4.92; p = 0.02). Our findings show that the N. meningitidis carriage rate in adolescents from Salvador, Bahia, is low and is potentially influenced by the low prevalence of N. meningitidis genogroup C. However, continued surveillance is important to identify changes in the dynamics of N. meningitidis, including the emergence of diseases due to a non-C serogroup.