IMPACT OF VARICELLA VACCINATION IN CHILDREN UNDER 1 YEAR OF AGE IN ITALY (2006-2011)

INTRODUCTION Varicella represents the most widespread vaccine preventable childhood infectious disease in Italy. In children under 1 year of age, it tends to be more severe with a higher rate of complications like pneumonia, hepatitis and encephalitis, and is associated with higher mortality. In Italy, between 2003 and 2010, 8/21 Regions have progressively introduced Universal Varicella Vaccination (UVV) in their immunization programs, with different schedules in children aged 13-15 months and 5-6 years. Objective of this study was to analyze hospitalization rates (HR) in children under 1 year of age, by the different vaccination policies in Italy in 2006-2011. PATIENTS AND METHODS We performed a retrospective review of hospitalization data from Italian hospital discharge forms, provided by the Ministry of Health. We considered the codes 052.0-052.9 by ICD9- CM system (primary or secondary diagnosis). HR of varicella in children under 1 year of age were calculated by different vaccination policies (referring to the year 2008) in 3 different areas: area 1, with a UVV policy (Veneto, Sicilia, Puglia, Toscana), area 2, with policy of vaccinating susceptible adolescents and at-risk population (Piedmont, Friuli Venetia Giulia, Liguria, Lazio, Campania, Basilicata, Calabria, Sardinia) and area 3 with vaccination of only at-risk population (the remaining regions). The denominator for HR was calculated using resident population aged less than 1 year numbers according to ISTAT. RESULTS 10,483 hospitalizations for varicella were identified in patients of any age. The peak in varicella hospitalizations was observed in the first year of life. In this age group varicella was responsible of 13.7% of hospitalizations. 71.5% of cases in primary diagnosis (PD) were varicella without mention of complications, followed by the varicella with other specified complication (9.6%). 32 diagnosis reported post-varicella encephalitis and 15 hemorrhagic pneumonia. When varicella diagnosis was reported as secondary (SD), the most frequent PD were pneumonia or respiratory failure (25.7%). Annual HR globally declined in this age group from 56.4 to 34.2/100,000 children. The greatest HR were in area 3 and they declined from 63.9 to 44/100,000. In area 2 HR declined from 55.6 to 43.1/100,000, and in area 1 HR significantly decreased from 49.3 to 11.5/100,000 (test for trend, p < 0.001) (Fig. 1). CONCLUSIONS This study demonstrated that varicella continues to represent a relevant health problem in Italy, especially in the pediatric age. Data obtained by the Italian Regions that first introduced universal vaccination demonstrated that it allows to reduce the incidence of varicella and hospitalization rates.