Incidences of new hepatitis B infection and anti‐hepatitis B core‐negative occult hepatitis B infection among Japanese blood donors in relation to anti‐hepatitis B surface antigen levels

Abstract A transfusion‐transmitted hepatitis B virus (HBV) infection caused by blood only positive for anti‐hepatitis B surface antigen (anti‐HBs) was reported. Occult HBV infection (OBI) with sole anti‐HBs among blood donors is an issue. The incidence of HBV infection among repeat blood donors was investigated with a detailed HBV infection phase, focusing on the influence of anti‐HBs level. This study followed 3 435 653 donors for HBV DNA conversion over 4 years and 9 months. Infection phase was determined based on marker changes over DNA conversion. This study identified 115 hepatitis B surface antigen (HBsAg) conversions, 72 DNA‐only conversions, and 15 DNA plus anti‐hepatitis B core (anti‐HBc) conversions among donors all negative for HBV DNA, HBsAg, and anti‐HBc. Total incidence was 2.38/100 000 person‐years (PY). None of these 202 new HBV infections arose in the group with anti‐HBs titer ≥ 10 mIU/mL. In total, 30 anti‐HBc‐negative OBIs were identified (incidence; 0.35/100 000 PY); 7 showed typical secondary anti‐HBs response, and 23 showed stable anti‐HBc and anti‐HBs levels at DNA conversion. The HBV infection‐protective ability of anti‐HBs ≥ 10 mIU/mL was reinforced. In addition to new infections, the blood donor population includes anti‐HBc‐positive‐ and negative OBI with immune reactions or abortive HBV infection.