Background: Thalassemia is hereditary anemia with lifelong transfusion as treatment and hepatitis B virus (HBV) infection is one of the transfusion transmitted infections (TTI). HBV vaccination is obligatory for these patients by 3 double-dose injections. The authors studied the HBV status and immune response to vaccination by hepatitis B surface antibody (HBsAb) titration in their thalassemic patients. They also compared these results with their previous study to find out the effectiveness of a booster dose in the immunity of patients against HBV.
Materials and methods: Hepatitis B surface antigen (HBsAg), HBsAb, and hepatitis B core antibody (HBcAb) were detected in sera of 416 patients at the Tehran Adult Thalassemia Clinic. The immune status was classified into 4 categories: (1) immune to HBV via the vaccination (positive vaccinal)--if HBs Ag: negative, HBsAb: positive, HBcAb: negative; (2) immune to HBV via the natural disease (past infection)--if HBs: negative, HBsAb and HBcAb: both positive; (3) nonimmune to HBV (negative)--if all three parameters were negative; (4) carrier of HBV (carrier state)--if HBs Ag was positive and HBsAb and HBc Ab: both negative. Also grading of immunity done by HBsAb titration as positive if HBsAb titer was more than 100 IU/mL, negative if HBsAb titer was less than 10 IU/mL, and weakly positive if antibody level was 10-100 IU/mL.
Results: There were 416 patients: 302 (72.5%) with thalassemia major (TM), 104 (25%) thalassemia intermedia (TI), 7 (1.6%) sickle thalassemia (ST), and 3(0.7%) alpha-thalassemia (HbH disease). The mean age was 25.6 +/- 8.3 yr and median age was 24 yr; there were 247 (59.4%) males and 169 (40.6%) females. A total of 257 patients (61.7%) were splenectomized. According to our classification 289 (69.4%) were immunized by vaccination; 80 (19.2%) were immunized by past infection; 44 (10.5%) were negative, and 3 (0.7%) were in carrier state of HBV. In grading of immunity to HBV vaccination, 319 (76.6%) patients had HBsAb > 100 IU/mL (positive), 77 (18.5%) between 10 and 100 IU/mL (weakly positive), and 20 (4.8%) less than 10 IU/mL (negative). There was no significant correlation between the level of HBsAb and splenectomy or type of thalassemia.
Conclusion: Response rate to vaccination is more than 95% after complete course (3 doses) in healthy individuals but failure to fulfill vaccination seems a problem in chronic transfused patients. These results reflect advantages of a booster dose of vaccine, which increased the protection level among these high-risk patients from 46.9% (in the authors' previous data) up to 69.4% in this study.