Investigation (In Vivo and In Vitro) of Booster Dose Vaccine Requirement for Long-Term Protection against Hepatitis B Virus Infection

Aim: Studies have shown that no booster dose was required at least 10 to 15 years after a primary vaccination for individuals who developed protective anti-hepatitis B surface (anti-HBs) antibodies. In this study, booster dose requirement for HBV after primary immunization was investigated. Materials and Methods: Seventeen individuals vaccinated previously were enrolled in the study. They had once developed a protective level of anti-HBs antibody after immunization and their anti-HBs titer had declined to an underprotective level. Twenty uninfected and unvaccinated healthy people were chosen as controls.Lymphoproliferative response to in-vitro stimulation with hepatitis B surface antigen (HBsAg) and anti-HBs response to vaccine were evaluated for immune response. Results: T lymphocytes from 4 (24%) of the study group showed lymphoproliferative response to HBs Agstimulation while none of the controls did (P 0.05). In all subjects in the study group, anti-HBs response(=10 mIU/ml) was detected 1 to 7 days after the booster injection but in only 2 of the controls antibody response was detected 28 days after the first dose of HBV vaccine (P 0.0001). Conclusions: A booster dose of HBV vaccine might not be required because of immunological memory.