Immune response to hepatitis B vaccination in drug using populations: a systematic review and meta-regression analysis.

Injecting and non-injecting drug users are at increased risk of contracting HBV infection, and show lower antibody response to hepatitis B vaccination compared to the general population. This systematic review and meta-regression analysis aimed to estimate seroprotection rates and identify host or vaccine factors associated with varying immune response following hepatitis B vaccination in drug using populations. Original research articles were searched using online databases (Medline, PubMed, and Embase) and from reference lists of eligible articles. HBV vaccine intervention studies reporting seroprotection rates in drug users, published in English during or after 1989 were eligible. Of 978 citations reviewed, 11 studies were eligible and included for final analysis. The reported seroprotection rates ranged from 54.5% to 97.1%. The studies were significantly heterogeneous (Q=180.850, p=0.000). Measurement of anti-HBs antibody at 2 months after the third vaccine dose (RR=2.62, 95%CI=1.16-5.94, p=0.026) was significantly associated with higher seroprotection rates compared to measurement at 1 month and 6 month following third vaccine dose. Age, gender, current drug use, vaccine dose and schedule, anti-HBc, anti-HCV and anti-HIV antibody seropositivity, and proportion of IDU study population did not show a significant association with seroprotection rates. Recommendations for future research include the definition of a standardized time point for the measurement of anti-HBs antibody levels, to enhance comparability of the immune response between different studies. Studies should strive to accurately report all potentially relevant factors affecting immune response to vaccine. Long-term follow up studies are needed to assess the seroprotection status in drug using populations receiving hepatitis B vaccine by standard or accelerated schedules.