Varicella vaccination as useful strategy for reducing the risk of varicella-related hospitalizations

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Abstract Introduction The present study summarizes evidences of the impact of varicella vaccination (VV) on hospitalization rates attributable to this infectious disease in Italy. Methods We have carried out a retrospective observational study that analysed hospital discharge records and VV coverage at 24 months collected from 2003 to 2018 by the Italian Health Ministry. All hospitalizations with the presence of an ICD-9 CM 059.X code in the principal diagnosis or in any of the five secondary diagnoses were considered as related to varicella. The hospitalization rate reduction was evaluated by calculating average annual percent change (AAPC) through joint-point analysis. Results Hospitalization rates showed a decreasing risk by age: children aged <1 year were the most affected age group in each region (42.56/100,000 per year), whereas lower incidence rates were found in older age groups (23.76/100,000 in 1 to 5 years age group and <4/100,000 in the following groups). Varicella hospitalization rates decreased significantly after the introduction of VV (3.42 vs. 2.67 per 100,000; P < 0.001). During the first five years after vaccination introduction hospitalization rates showed a statistically significant decrease especially for infants aged <1 year (AAPC -34.98%; p < 0.001) and 1 to 5 years old (AAPC -35.22%; P < 0.01). VV coverage was strongly correlated with hospitalization rates decrease over each paediatric age group (R-squared 0.38 in aged <1 year, p < 0.001; 0.71 in 1 to 5 years old, p < 0.001; 0.93 in 6 to 14 years old, p < 0.0001). Conclusions All the previously reported findings confirm that hospitalization rates are strictly related to both the number of years since vaccination introduction and the vaccination coverage. VV confirms to be an important step in public health strategies and the introduction of universal vaccination, with high vaccination coverage, should be considered as an extremely powerful tool for reducing the risk of complications. Key messages This study adds update findings to the literature and shows that varicella hospitalizations in Italy, from 2003 to 2018, have reduced their burden, that was high in years before varicella vaccination. Varicella vaccination introduction and high coverage are powerful tools for reducing the risk of varicella complications and related hospitalizations in the general population.