RESUMO
The artificially acquired humoral immunity against hepatitis B virus (HBV) apparently may decline over the years. This study aimed to investigate the prevalence of naturally occurring serological markers of infection and active immunity to HBV in severely ill children and adolescents treated at the Martagão Gesteira Pediatric Hospital who received blood transfusions. The serum samples of 353 children who received poly-transfusions between August 2016 and March 2017 were tested for HBV surface antigen (HBsAg) markers, anti-HBc antibodies (IgG and IgM isotypes), and IgG anti-HBs. None of the children presented an outcome compatible with HBV infection. Three patients were seroreactive to markers of past infection, tested positive for anti-HBc IgG and negative for anti-HBc IgM, and were seropositive for anti-HBs, with antibody titers of >150.00 mIU/mL. Only 52.4% of the patients in the study were protected against HBV, with anti-HBs antibody titers of >10 mIU/mL. Children aged 5 years had lower titers of anti-HBs. The results indicated that the older children were more likely to be unprotected from HBV; this suggests the need to evaluate the vaccine response in children, especially those who received blood transfusions.