Impact of meningococcal C conjugate vaccination four years after introduction of routine childhood immunization in Brazil.

BACKGROUND: Routine infant immunization with meningococcal C conjugate (MCC) vaccination started in Brazil in November 2010, scheduled at three and five months plus a booster at 12-15months of age. No catch-up was implemented. We assessed the impact of vaccination on meningococcal C disease (MenC) four years after vaccination start in the National Immunization Program. METHODS: We performed an ecological quasi-experimental design from 2008 to 2014 using a deterministic linkage between the National Notification and the National Reference Laboratory databases for meningitis. We conducted an interrupted time-series analysis considering Brazil except for Salvador municipality, because an epidemic of serogroup C disease occurred in this city, which prompted a mass vaccination campaign with catch-up for adolescents in 2010. Observed MenC rates in the post-vaccination period were compared to expected rates calculated from the pre-vaccination years. Results for Salvador were presented as descriptive data. An additional time-series analysis was performed for the state of São Paulo. RESULTS: A total of 18,136 MenC cases were analyzed. The highest incidence rates were observed for infants aged <12months and no second incident peak was observed for adolescents. For Brazil, MenC rates were reduced by 67.2% (95%CI 43.0-91.4%) for infants <12months of age, 92.0% (77.3-106.8%) for the age-group 12-23months, and 64.6% (24.6-104.5%) for children aged 2-4years. For children 5-9years old, MenC rates reduced 19.2% (9.5-28.9%). Overall, 955 MenC cases were averted in Brazil in individuals aged <40years after MCC vaccination. Results from São Paulo State, mirror the patterns seen in Brazil. CONCLUSION: After four years of infants and toddlers vaccination start, MenC invasive disease reduced in the target population. This investigation provide a robust baseline to ascertain how much the upcoming catch-up dose in 12-13years of age will accelerate the decrease in MenC incidence rates among youths in Brazil.