Immunogenicity, reactogenicity and adherence to a combined hepatitis A and B vaccine in illicit drug users

The use of illegal drugs is associated with an increase in infective risk for the hepatitis viruses, against which the vaccination of drug users (DUs) is recommended unanimously. The aim of the study was to determine tolerability, adherence and immune response of a combined vaccine providing dual protection against hepatitis A virus (HAV) and hepatitis B virus (HBV).

The vaccine was administered to 38 DU, attending three public health centres for drug users in northern Italy, with a three-dose schedule (at 0, 1 and 6 months). The vaccine was well tolerated: only one adverse reaction (fever) was recorded after the 110 doses administered (0.9%). The vaccine schedule was completed successfully in 35 cases (92.1%). At month 8, in 34 subjects (89.5%) antibody response was evaluated: all showed seroprotection for HAV and in 33 subjects (97.1%) for HBV.

The vaccine, studied for the first time in DUs, proved to be safe, well accepted and immunogenic; anti-HAV response was 1272 mIU/ml and 1726 mIU/ml for anti-HBV, titres lower than reported in literature for the general population. This study suggests that DUs who are HAV/HBV-negative could be vaccinated with combined vaccine.