Prevalence of and trends in hepatitis B virus infection

The presence in the blood of antibodies to a virus indicates that someone has at one time been infected with or vaccinated against the virus. In contrast to HIV and HCV, there is an effective vaccine against hepatitis B virus (HBV). Thus, in the case of HBV, the proportion of IDUs who do not have antibodies (aHBs or aHBc) against the virus constitutes the potential vaccination population and is an important indicator of the need for a vaccination programme. In the EU, there is greater variation in the proportion of drug users who have (any type of) antibodies against HBV than in those with antibodies to HCV. Throughout the EU, approximately 20–60 % of IDUs have antibodies against hepatitis B, suggesting a large potential for vaccination programmes directed at IDUs (40–80 %).

Current hepatitis B infection, as indicated by the presence in the blood of a serological marker called HbsAg, can be either recent or chronic. High levels of current infection suggest a risk of a high future level of severe, long-term complications and of widespread transmission to others through high-risk injecting behaviour or unsafe sex. The prevalence of current HBV infection is recorded in only a few countries, but appears to differ widely and in some cases is high.