Distribution of invasive meningococcal B disease in Italian pediatric population: implications for vaccination timing.

Neisseria meningitidis group B (MenB) is a leading cause of meningitis and sepsis. A new vaccine has been recently licensed. The aim of the present study was to evaluate the epidemiology of MenB disease in pediatric age and define the optimal age for vaccination. All patients aged 0-18 years admitted with a diagnosis of meningitis or sepsis to the 83 participating Italian pediatric hospitals were included in the study. Blood and/or cerebrospinal fluid (CSF) samples were tested by Realtime-PCR and/or culture. One hundred and thirty-six cases (mean age 5.0 years, median 2.7) of MenB disease were found. Among these, 96/136 (70.6%) were between 0 and 5 years, 61/136 (44.9%) were between 0 and 2 years. Among the latter, 39/61 (63.9%) occurred during the first year of life with highest incidence between 4 and 8 months. A case-fatality rate of 13.2% was found, with 27.8% cases below 12 months. Sepsis lethality was 24.4%. RT-PCR was significantly more sensitive than culture: 82 patients were tested at the same time by both methods, either in blood or in CSF; MenB was found by RT-PCR in blood or CSF in 81/82 cases (98.8%), culture identified 27/82 (32.9%) infections (Cohen's Kappa 0.3; McNemar's: p<10⁻⁵). The study shows that the highest incidence of disease occurs in the first year of age, with a peak between 4 and 8 months of life; 30% of deaths occur before 12 months. The results suggest that the greatest prevention could be obtained starting MenB vaccination in the first months of life; a catch-up strategy up to the fifth year of life could be considered. Our results also confirm that Realtime PCR is significantly more sensitive than culture. In those countries where only isolate positive infections are counted as cases, the incidence of MenB infection results highly underestimated.