An assessment of the effect of hepatitis B vaccine in decreasing the amount of hepatitis B disease in Italy

Background. Hepatitis B (HBV) infection is an important cause of morbidity and mortality and it is associated to a higher risk of chronic evolution in infected children. In Italy the anti-HBV vaccination was introduced in 1991 for newborn and twelve years old children. Our study aims to evaluate time trends of HBV incidence rates in order to provide an assessment of compulsory vaccination health impact. Method. Data concerning HBV incidence rates coming from Acute Viral Hepatitis Integrated Epidemiological System (SEIEVA) were collected from 1985 to 2006. SEIEVA is the Italian surveillance national system that registers acute hepatitis cases. Time trends were analysed by joinpoint regression using Joinpoint Regression Program 3.3.1 according to Kim's method. A joinpoint represents the time point when a significant trend change is detected. Time changes are expressed in terms of the Expected Annual Percent Change (EAPC) with 95% confidence interval (95% CI). Results. The joinpoint analysis showed statistically significant decreasing trends in all age groups. For the age group 0-14 EAPC was -39.0 (95% CI: -59.3; -8.4), in the period up to 1987, and -12.6 (95% CI: -16.0; -9.2) thereafter. EAPCs were -17.9 (95% CI: -18.7; -17.1) and -6.7 (95% CI: -8.0; -5.4) for 15-24 and ≥25 age groups, respectively. Nevertheless no joinpoints were found for age groups 15-24 and ≥25, whereas a joinpoint at year 1987, before compulsory vaccination, was highlighted in 0-14 age group. No joinpoint was observed after 1991. Discussion. Our results suggest that the introduction of compulsory vaccination could have contribute partly in decreasing HBV incidence rates. Compulsory vaccination health impact should be better investigated in future studies to evaluate the need for changes in current vaccination strategy.