Long term response to mandatory anti-HBV vaccination: risk for disease acquisition and opportunities for re-vaccination within the ICONA cohort.

• Italy was traditionally considered a Country with an intermediate prevalence for HBV infection, with HBsAg positivity ranging between 1.6 and 3.4% (with areas topping to 5.6%). • HBV incidence and prevalence started to decrease during the 1980s for the improvement of socio-economic conditions, the change in medical procedures, a better knowledge of local transmission routes and the availability in 1983 of a vaccine for key populations such as intravenous drug users (IVDU), men who have sex with men (MSM), patients undergoing hemodialysis and healthcare workers. • In 1991, the law n. 165 introduced mandatory HBV vaccination for all people born after 1979 through two different cohorts (Figure 1): • Born between 1979 and 1991: vaccinated at their 12th birthday; • Born after 1992: vaccinated at their 1st birthday. • The rate of vaccination response is generally 90 to 95%, but 20 years after vaccine administration the coverage drops to 60%. • In adult HIV-positive individuals who received the vaccination after HIV infection, the response rate is below 30% seven years after vaccine administration. • According to the Ministry of Health, vaccination coverage in Italy has always been around 95%.