Objective: To describe the trend of invasive pneumococcal disease in the years 2008-2014; to verify the impact of the conjugate vaccine and monitor the occurrence of serotype replacement.
Design: Prospective observational study based on data from the national surveillance for invasive bacterial diseases coordinated by the Istituto superiore di sanità.
Setting and participants: Seven Italian regions (A.P. Bolzano, A.P. Trento, Emilia-Romagna, Friuli-Venezia Giulia, Lombardia, Piemonte, Veneto), accounting for 43% of the national population.
Main outcome measures: Number of cases and incidence of invasive pneumococcal diseases: global, stratified by age groups and by serotypes included or not in the PCV13.
Results: In 2008-2014, in the 0-4 age group IPD incidence for all serotypes decreased from 7.1 to 2.9/100,000; incidence for vaccine serotypes (VT) decreased from 5.5 to 1.1/100,000, while incidence for non-vaccine serotypes (NVT) increased from 1.6 to 2.0/100,000 (2.5 in 2013). In the >64 age group, IPD incidence increased from 5.3 to 7.5/100,000; VT incidence decreased from 3.9 to 3.2 (4.9 in 2010 and 4.3 in 2013), whereas NVT incidence increased from 1.4 to 4.4/100,000.
Conclusion: Use of the conjugate vaccine has reduced the number of cases of IPD by VT in children; the increase in IPD by NVT, above all in older age groups, suggests a serotype replacement.