IMMUNE STATUS AND THE IMMUNE-RESPONSE TO HEPATITIS-B VIRUS-VACCINE INTHALASSEMIC PATIENTS AFTER ALLOGENEIC BONE-MARROW TRANSPLANTATION

We evaluated the immune status with respect to HBV and the immune resp onse to readministration of HBV vaccine in a series of 20 patients wit h homozygous beta-thalassemia, aged 6-23 years (mean age: 13.0 +/- 4.2 ) who had undergone allogeneic bone marrow transplantation (BMT). Thir teen of them (group A), had received three doses of plasma-derived HBV vaccine from 7 to 5 years before BMT and 4-5 weeks after the last dos e of vaccine, they had had high serum levels of HBV antibodies (anti-H Bs). The remaining seven patients (group B) had had clinical symptoms and laboratory evidence of HBV infection in childhood with markedly el evated serum of anti-HBs. Before revaccination, a significantly lower percentage of patients (P < 0.005) with seropositive levels of anti-HB s was observed in group A than in group B. After administration of the second dose of HBV vaccine the percentage of subjects with protective levels of anti-HBs rose to 100% in both groups of patients even if th e geometric mean of titers of anti-HBs increased more significantly in group B patients than in group A. We conclude that the serum levels o f anti-HBs afforded by HBV vaccine administered from 7 to 5 years prev iously are very low and probably non-protective in most beta-thalassem ic patients after allogeneic BMT, and that at least two doses of HBV v accine should be readministered from 18 to 24 months after BMT to achi eve adequate and long-term protection from HBV.