Complementary Presence of HBV Humoral and T-cell Response Provides Protective Immunity after Neonatal Immunization

Background and Aims: Hepatitis B vaccination is the most cost effective way to prevent hepatitis B virus (HBV) infection. Hepatitis B vaccine (HepB) efficacy is usually assessed by anti-hepatitis B surface antigen (HBsAg) level, but there are few reports of humoral and cellular immune responses to HepB in children after neonatal vaccination. Methods: A group of 100 children with a history of primary hepatitis B immunization were included in this study to evaluate the efficacy of HepB. Blood samples were obtained from 80 children before, and 41 children after, a single HepB booster dose. Children with low anti-HBsAg (HBs) titers of < 100 mIU/mL received a booster dose after giving their informed consent. Anti-HBsAg, T-cell response and percentage of B-cell subsets were assayed before and after the booster. Results: Of the 80 children, 81.36% had positive T cell and anti-HBsAg responses at baseline. After the booster dose, the anti-HBsAg titer (p < 0.0001), positive HBsAg-specific T-cell response (p=0.0036), and spot-forming cells (p=0.0003) increased significantly. Compared with pre-existing anti-HBsAg titer < 10 mIU/mL, the anti-HBsAg (p=0.0005) and HBsAg-specific T-cell responses (p < 0.0001) increased significantly in preexisting anti-HBsAg titer between 10 and 100 mIU/mL group. Change of the HBV-specific humoral response was the reverse of the T-cell response with age. Peripheral blood lymphocytes, B cells, and subset frequency decreased. Conclusions: HBV immunization protection persisted at least 13 years after primary immunization because of the complementary presence of HBV-specific humoral antibodies and a T-cell immune response. One dose of a HepB booster induced protective anti-HBsAg and promoted an HBsAg-specific T-cell response. In HBV endemic regions, a HepB booster is recommended to children without anti-HBsAg because of effectiveness in HBV prevention.