Il ruolo della vaccinazione nella prevenzione dell'epatite virale di tipo B: Aspetti storici ed attualita

Viral hepatitis B remains a major public health problem in many parts of the world in which is still a leading cause of acute and chronic liver disease including chronic active hepatitis, cirrhosis, and hepatocellular carcinoma. WHO estimates that nearly 1 million people die each year from HBV- related diseases, that about 2 billion people in the world have been infected and that more than 350 million individuals are chronic carriers of the virus. Age at the time of acquisition of HBV is a major determinant of chronicity. In areas of high endemicity, in which most people become infected during childhood and are at increased risk of becoming chronic carriers of HBV and of developing cirrhosis and hepatocellular carcinoma, universal vaccination of newborns is the proper strategy for long-term control of hepatitis B. Thus, the integration of HB vaccination into the framework of the WHO-EPI must be considered a priority. According to WHO recommendations all countries should incorporate HB vaccination into their national programs. Ideally, universal combined infant and early adolescent immunization, together with the vaccination of high risk groups should be applied where economically feasible. As of 1997, more than 90 countries have instituted national policies. Starting from 1991, hepatitis B vaccination became mandatory for all infants and 12-years old adolescents in Italy. Since the beginning of this program, vaccine has been given to more than 6 million children with an outstanding record of safety and efficacy. In high-endemic countries as Taiwan, Alaska and the Gambia, vaccination of newborns has been shown to be effective in providing a dramatic decrease of HBV transmission. Studies carried out in Taiwan have demonstrated that the incidence of hepatocellular carcinoma has initiated to reduce in vaccinated children aged 6-14 years. Due to the long-term protection induced by vaccination, routine administration of booster doses to healthy, immunocompetent individuals is currently not recommended as a public health measure.