A surveillance system of Invasive Pneumococcal Disease in North-Eastern Italy

From 2007, in the Veneto Region (Italy), a surveillance system for invasive pneumococcal diseases (IPD) was implemented to estimate the regional epidemiology of IPD and to evaluate the impact of 13-valent pneumococcal conjugate vaccine (PCV13) vaccination.

Data were collected from 2007 to 2014 and the total, annual and age-specific IPD notification rates were calculated. A Poisson regression model was used to identify the possible risk factors for developing IPD.

A total of 713 IPD cases were notified and the overall IPD notification rate was equal to 2.0 cases per 100,000 population (95% CI: 1.7-2.1), with an increasing trend between 2007 and 2014. The pneumococcal serotypes were identified in 608 (85.3%) isolates from biological specimens, and the most distributed serotypes were those contained in PCV13. Children <5 year-old and the adults over 65 year-old showed the highest PCV13 vaccine-type IPD notification rate, equal to 2.7/100,000 and 2.8/100,000, respectively. The risk to develop IPD was greater in children aged <5 years (RR = 8.9, 95% CI: 5.1-15.9; p<0.0001) and in adults aged >65 years (RR = 4.3, 95% CI: 2.7-6.9; p<0.0001), especially in males > 65 years of age (RR = 1.7, 95% CI: 1.0-2.8; p = 0.042). The invasive pneumococcal disease was mainly caused by the PCV13 serotypes (RR = 2.9, 95%CI: 2.3-3.9; p<0.0001), principally after the PCV13 introduction (RR = 2.3, 95% CI: 1.4-3.8; p<0.001). In spite of that, a significant reduction of the overall IPD incidence is evident in the period following the PCV13 vaccine introduction (RR = 0.4, 95% CI: 0.3-0.5; p<0.0001), particularly in children aged <5 years (RR = 0.3, 95% CI: 0.2-0.7; p = 0.002), demonstrating the real efficacy of PCV13 immunization for children.

In the Veneto Region, the surveillance system has allowed to describe the detailed epidemiological profile of invasive pneumococcal disease, pointing out that the most circulating pneumococcal serotypes were those contained in the PCV13 vaccine.