Burden of varicella in Italy, 2001-2010: analysis of data from multiple sources and assessment of universal vaccination impact in three pilot regions.

Varicella represents the most widespread vaccine-preventable childhood infectious disease in Italy. The purpose of this retrospective study was to assess the burden of varicella in Italy and in three regions that first implemented universal varicella vaccination. Four data sources were analysed: statutory notification data, the National Hospital Discharge Database, mortality data, and the vaccination coverage reached in Sicilia, Veneto and Apulia. The incidence rates per 100,000 population were calculated using the Italian resident population provided by the Italian Institute of Statistics in 2001-2010. In 2001-2010, the mean annual incidence of notifications of varicella was 150.7 cases per 100,000 population, reaching 948.6 cases per 100,000 population in the paediatric age group. The annual incidence declined to 102.6 per 100,000 population in 2010. During the period considered, 20,295 hospitalizations for varicella were observed. The mean annual incidence was 3.4 per 100,000 population, reaching a minimum of 2.5 per 100,000 in 2009 and 2010. Of the hospitalizations, 68.4% occurred in the paediatric age group. The median length of hospital stay was 4 days. During 2001-2003 and 2006-2010, 33 deaths were reported. In the three regions considered, vaccination coverage increased steadily, reaching 81.5% in Sicily, 79.4% in Veneto and 75.6% in Apulia in 2010. During the same period, hospitalization and notification rates decreased significantly. This study demonstrated that varicella continues to represent a relevant health problem in Italy, especially in the paediatric age group. Data obtained from the three Italian regions that first introduced universal vaccination demonstrated that vaccination reduces the incidence of varicella and hospitalization rates.