Long-term antibody response and immunologic memory in children immunized with hepatitis B vaccine at birth

ABSTRACT

To evaluate the long-term immunity and immunologic memory provided by universal hepatitis B vaccination program at birth, and to evaluate the booster effects of different dosages of hepatitis B vaccine on children, who lost protective antibody titers to hepatitis B surface antigen [HBs -Ag], this study was conducted. Community-based sero-epidemiologic study was done on 453 healthy 10.5 years old Iranian children, one decade after implementation of a mass hepatitis B vaccination program. A booster vaccination with different dosages was given for children who did not have protective level of anti-hepatitis B surface antigen antibody [anti-HBs]. Quantitative serologic responses to different dosages of vaccine were compared using X[2] statistical test. A total of 42% children [191 of 453] children had low concentration [<10IU/L] of anti HBs antibody, 18.5% [84 of 453] were susceptible [antibody titer <2IU/L]. 87.2% of 165 nonprotected-boostered vaccines showed immunologic memory to different doses of booster, and developed protective antibody titer two weeks later. The differences between pre- [3.48 +/- 3.39; mean +/- SD] and post- [153 +/- 163.84] vaccination antibody titers were significant [p=0.000]. Antibody titers achieved by different doses of vaccine had significant proportion to vaccine doses. No hepatitis B infection markers were detected in those children who were not sero-protected and did not respond to booster dose of vaccination. According to these findings, universal hepatitis B vaccination program at birth provides adequate protection against hepatitis B virus infection at least for 10 years. It might suggest that booster vaccination is not recommended, but further follow-up studies at adulthood age group are recommended