Reduction in Neisseria meningitidis infection in Italy after Meningococcal C conjugate vaccine introduction: A time trend analysis of 1994-2012 series

The incidence of invasive meningococcal disease (IMD) In Italy is among the lowest in Europe. Meningococcal C conjugate vaccine (MCC) was introduced in 2005 for 12 onths old infants. The aim of this study was to describe the epidemiology of IMD in Italy from 1994 to 2012 and to evaluate the impact of MCC introduction. Data about Neisseria meningitidis (N. meningitidis) cases were drawn from the National Surveillance of Invasive Bacterial Diseases. The average incidence of IMD during 1994-2012 in Italy was 0.36 per 100,000 (95%CI 0.30-0.40). N. meningitidis B was the most frequent serogroup and infants less than 12 onths old were the most affected. Joinpoint analysis showed a statistically significant reduction in the incidence of N. meningitidis C related IMD after MCC introduction: the Annual Percentage Change declined from 21.8 (95%CI 15.1; 28.9) in 1994-2005 to -19.9 (95%CI -28.2; -10.7) afterwards. No changes were observed with respect to N. meningitidis B related IMD. Poisson regression showed a statistically significant reduction in the incidence of IMD both associated to N. meningitidis C (Incidence Rate Ratio 0.33; 95%CI 0.29-0.37) and due to all serogroups (Incidence Rate Ratio 0.70; 95%CI 0.65-0.75) in the post-vaccination period compared to the pre-vaccination one. On the other hand, the incidence of N. meningitidis B related IMD did not decrease. Our results suggest that MCC had an impact in decreasing the incidence of N. meningitidis C related IMD. However, data on typing are incomplete and efforts are needed to make them available for studying the need and the impact of other meningococcal vaccines.