Incidence surveillance of invasive pneumococcal disease in children under five years of age in Lombardy (Northern Italy)

Background and aims: The incidence rate of invasive pneumococcal disease (IPD) varies across geographical areas; in Italy only local studies have been conducted. The aim of this study is to estimate the IPD incidence in the Lombardy region, Northern Italy, and to identify the circulating S. Pneumoniae serotypes. Methods: An observational, prospective, multicentric, population-based active surveillance system of IPD and pneumococcal serotyping ranging from 01 September 2008 to 31 December 2010 recruited children < 5 years with suspected IPD at emergency room visit in 10 hospitals, and involved one central laboratory for antimicrobial sensitivity and serotyping of isolates (culture and PCR analyses). Results: A total of 251 children (55,8% males) with suspected IPD was recruited (47,4% aged < 24 months). Data on IPD status were available in 236 (94,0%) children. 20 children (8,5%) had S.pneumoniae isolated (9 cases aged< 24 months). The pooled annual incidence rate of IPD was estimated around 28,9/100.000 (95% CI). Pneumonia was found in 11 cases (55%), sepsis in 2 (10,0%), meningitis in 1 (5,0%), bacteremia in 6 (30,0%). Strains included in the 13-valent vaccine accounted for 14 of 17 cases available for serotype determination; not included serotypes accounted for 3 cases (12B; 15C; 23B). Conclusions: PCV 13 showed serotype coverage rate in children aged < 5 years higher than PVC 7 coverage (82,3% vs. 29,4%). Vaccination by the 13-valent vaccine option might notably decrease the incidence of IPD.