Transfusion-transmitted HBV infection with isolated anti-HBs-positive blood.

Background: Hepatitis B virus (HBV)-positive individuals with isolated anti-HBs are found among HBV vaccine recipients and healthy blood donors with no vaccination history. HBV infectivity from blood transfusions derived from such individuals remains unclear.

Case Presentation: A male patient who received transfusion with blood negative for individual donation-NAT, HBsAg and anti-HBc but weakly positive for anti-HBs developed typical transfusion-transmitted (TT)-HBV with anti-HBc response. The responsible blood donor was a frequent repeat donor showing a marked increase in anti-HBs titer without anti-HBc response 84 days after index donation. Test results for his past donations showed transient viremia with very low viral load and fluctuating low-level anti-HBs. The HBV vaccination history of this donor was unknown.

Discussion: Anti-HBs and anti-HBc kinetics of the donor suggest a second antibody response to new HBV challenge, representing a vaccine breakthrough case. On the other hand, transient low-level viremia and fluctuating anti-HBs in the test results of past donations suggested chronic occult HBV infection with isolated anti-HBs.

Conclusion: Whatever the basic infection state, blood donors with isolated weak anti-HBs may include a small population with a risk of causing TT-HBV. Identifying individuals harboring such TT-HBV risk among individuals positive only for anti-HBs is difficult under current screening strategies. Active surveillance for the occurrence of TT-HBV with blood positive only for anti-HBs is necessary.