Universal hepatitis B immunization: infant, and infant plus adolescent immunization.

Hepatitis B virus (HBV) is one of the world's most widespread infectious agents and the cause of millions of diseases and deaths each year. Vaccination programmes aimed at risk groups are important for individual protection, but will not eliminate viral transmission in Europe, since 70% of acute hepatitis B cases are either acquired by sexual activity or are of unknown origin. In industrialized countries, HBV infection occurs mainly in young adults, however, when the virus is acquired during infancy it leads to extremely high rates of chronic carriership, contributing disproportionately to the overall pool of HBsAg carriers. This explains why integrating universal HB vaccination into routine infant immunization programmes is the best means for controlling HB in countries with intermediate to high levels of HB endemicity. In countries of low endemicity, universal immunization of adolescents may be considered as an alternative to infant vaccination, as this strategy has a more rapid effect on the epidemiology of the infection. Where feasible, a double strategy (infant plus adolescent) is the optimal solution. With this strategy, adolescent immunization is necessary only for the time required for the first cohort of immunized infants to reach adolescence. After universal vaccination programmes have been implemented, efforts must be made to sustain vaccine procurement, monitor coverage, check the incidence of acute disease, particularly in immunized cohorts and verify by seroepidemiological studies the progression made in the elimination of HBV transmission.