Lasting immune memory against hepatitis B in children after primary immunization with 4 doses of DTPa-HBV-IPV/Hib in the first and 2nd year of life

Immune memory was assessed in 301 children through administration of a challenge dose of monovalent HBV vaccine.At 4-5 years of age, 85.3% of subjects had persisting anti-HBs antibody concentrations ≥ 10 mIU/mL, rising to 98.6% after the HBV challenge dose. All but 12 subjects (95.8%) achieved post-challenge anti-HBs concentrations ≥ 100 mIU/mL. The post-challenge anti-HBs GMC rose by 100-fold compared to pre-challenge concentrations. An anamnestic response to the HBV vaccine challenge was observed in 96.8% of subjects, including 17/21 (81.0%) of children with initially undetectable antibodies (<3.3 mIU/mL). All but 4 of 42 subjects (90.5%) with anti-HBs antibodies <10 mIU/mL prior to the challenge dose, achieved seroprotective levels afterwards. A 4-fold rise in antibody concentration after the challenge dose was observed in 259/264 (98.1%) of initially seropositive subjects. The magnitude of the post-challenge responses was proportional to pre-challenge anti-HBs levels. No serious adverse events were reported during the study.The combined DTPa-HBV-IPV/Hib vaccine induced lasting immune memory against hepatitis B. Long term protection afforded by DTPa-HBV-IPV/Hib is likely to be similar to that observed following priming with monovalent HBV vaccines.http://www.clinicaltrials.gov webcite 106789 NCT00411697Achieving high routine vaccination coverage against hepatitis B in infancy is considered the highest priority for hepatitis B prevention by the World Health Organization (WHO) [1]. Universal Infant vaccination as the primary prevention strategy was adopted by the WHO in 1988 [2], after the failure of vaccination strategies targeting only at-risk groups [3,4]. Infant vaccination has the greatest impact on preventing chronic hepatitis B and its subsequent complications [1]. Furthermore, maintaining high vaccine coverage is more sustainable in infants than in adolescents who are difficult to reach and frequently poorly compliant [3,5-7].Combination vaccines for use in