Significance of Response to Hepatitis B Recombinant Vaccine in Subjects with Isolated Antibody to Hepatitis B Core Antigen

BACKGROUND It is important to differentiate whether isolated anti-HBc is due to false positive results or the prior exposure to hepatitis B virus, because individuals with false-positive anti-HBc can benefit from vaccination and their blood can be safely transfused. To distinguish between these two conditions, we evaluated the serologic response to hepatitis B vaccine. METHODS Ninety subjects with isolated anti-HBc (cases) and 100 subjects with totally negative hepatitis B serologic markers (controls) were recruited to receive three doses of hepatitis-B (HB) vaccine. Thirty days after the first dose of the vaccine, anti-HBs titers were checked and individuals with anti-HBs titer >50 mIU/mL did not receive additional doses of the vaccine. However, others completed the vaccination course, and another blood sample was collected 30 days after the third dose to measure anti-HBs level. RESULTS Nineteen (21.1%) cases and three (3%) controls had no sero-conversion (anti-HBs titers <10 mIU/mL) 30 days after the third dose (p<0.0001). Primary response, defined as the development of anti-HBs antibody titers ≥10 mIU/mL 30 days after the third dose, was observed in 43 (47.8%) cases and 92 (92%) controls (p<0.0001). Also, 31.1% of cases developed anti-HBs titers ≥ 50 mIU/mL 30 days after the first dose of vaccine, but the rate was significantly lower (5%) in the control group (p<0.0001). Furthermore, half of the individuals with positive isolated anti-HBc developed protective levels of anti-HBs after three doses of HB vaccination. CONCLUSION More than 75% of individuals with positive isolated anti-HBc can benefit from vaccination and can be included in donor pool. Also, one fifth seemed to have occult HBV infection. So HB vaccination may be used as a diagnostic tool for clarifying the situation of the subjects with isolated anti-HBc.