Impacto da vacinação contra o meningococo C na morbidade da doença meningocócica

Abstract

INTRODUCTION: Routine infant immunization with meningococcal C conjugate vaccine (MenC-V) started in Brazil in November 2010, administered at three, five and 12 months of age with no catch-up for older age-groups. However, by March 2010, a vaccination campaign with MenC-V was performed in Salvador in individuals under five years-old, and from 10 to 24 yearsold. In São Paulo state, the outbreaks occurred in teenagers and young adults prompting one-time vaccination campaign from 2010 to 2014 targeting these age-groups. OBJECTIVE: To assess the direct and indirect impact (herd effect) of vaccination on invasive meningococcal disease (MD) for capsular group C (MenC) four years after the introduction of MenC-V in three scenarios: i) Brazil as a whole (routine vaccination in childhood only); ii) Brazil except for Salvador (vaccination campaign with teenagers during the year of MenC-V introduction); and iii) São Paulo state (vaccination campaign for adolescents and young adults during 2010-2014 to control outbreaks). METHODS: We performed an ecological quasi-experimental design from 2008 to 2014 using data from the National Reference Laboratory for Meningitis, and data from the National Information System for Notifiable Diseases. A deterministic linkage was performed between the two databases to improve the accuracy of the detection of MD, especially in capsular groups. An interrupted time-series analysis was conducted using the Holt-Winters technique to control for pre-existing trends and seasonal variations. The MenC vaccination impact was evaluated as the percentage of reduction in the incidence rates of MenC in the post-vaccination period (2012 to 2014), using the pre-vaccination period (2008 to 2010) to estimate what would be expected on the post-vaccination period, whether the vaccination had not been introduced. For Salvador, we analyzed the effect of the vaccination on the number of MenC cases. RESULTS: A total of 18,136 invasive MD cases were analyzed. For Brazil as a whole, the vaccination reduced 67.4% (lower 95%CI 42.5%) the rates for MenC for infants under 12 months, 92.3% (lower 95%CI 77.7%) for the age-group 12-23 months, and 65.7% (lower 95%CI 28%) for children aged 2-4 years. Indirect impact (20-24.7%) was observed in the age-group 5-19 years. When excluding Salvador from the analysis of Brazil, the indirect impact was observed only for children in the age-group 5-9 years. In the scenario of São Paulo state, similarly to Brazil, significant impact was observed in the target age-groups, in addition to indirect impact in the age group 5-9 years. In Salvador, in addition to the effect on the vaccinated population a sharp and sustainable decline of MenC cases was observed in all age-groups not target for vaccination. Overall, 1,170 cases of MenC were averted in Brazil after the introduced of Men-C vaccination. CONCLUSION: The strategy of catch-up for adolescents and young adults, especially during the year of MenC-V introduction may lead to rapid and sustainable herd effect.