Quality of HBsAg-specific immune memory: response to hepatitis-B-revaccination in adolescents 10 – 15 years after immunization in infancy

Introduction: According to the recommendations of the German Standing Committee on Vaccination (STIKO) infants are vaccinated within the first two years, with no routine booster dose in later life. Thus, up to 50% of individuals lose protecting antibodies within 10 to 15 years, becoming again susceptible to hepatitis B infection. However, the presence of immune memory leading to an anamnestic immune response after contact with hepatitis B virus should protect these individuals against hepatitis B disease.

Study population, material and methods: To analyse the quality of HBsAg-specific immune memory after vaccination in infancy we studied the kinetics of specific antibodies after a booster dose of hepatitis B vaccine in adolescents whose anti-HBs level had dropped below 10 IU/l. 82 adolescents 14 to 18 years old were tested for anti-HBs 10 to 15 years after infant immunization. Individuals with anti-HBs concentrations below 10 IU/l were offered a booster dose and the humoral immune responses followed at day 0, 3, 7, 14 and 28 after revaccination.

Results: Of the 82 study participants, 53 (65%) showed anti-HBs-levels ≥10 IU/l (10 – 646 IU/l, median 63 IU/l), whereas 29 (35%) had anti-HBs < 10 IU/l. 24 of the latter were revaccinated. 4 (17%) did not respond at all, 3 (13%) developed maximum anti-HBs levels < 100 IU/l (10.1, 13.3, 30.1 IU/l). The remaining 17 (71%) showed values from 142 to 15.000 IU/l (median, 1729 IU/l) 4 weeks after the booster dose. The earliest response was observed at day 7 (15 individuals). 8 vaccinees showed maximum titer at day 14, whereas in 12 the highest anti-HBs-concentration was seen at day 28.

Conclusion: In more than one third of individuals vaccinated in infancy anti-HBs dropped below 10 IU/l within 10 to 15 years. Revaccination resulted in a good response in 71%, however 29% showed no (4/24) or only very low (3/24) anti-HBs-values after a booster. Thus, in 7/82 (8.5%) of our study participants the quality of the immune memory seems questionable.