Abstract
Protection against hepatitis B disease relies on either protective serum antibodies or on the ability of the immune system to mount an anamnestic response when confronted with the hepatitis B virus (HBV). This open multicenter study (EUDRACT: 2010-022538-10) measured antibodies to HBV surface antigen (anti-HBs) in 7-8-year-old children who had received 4 doses of hexavalent diphtheria-tetanus-acellular pertussis-HBV-inactivated poliovirus-Hemophilus influenzae type b conjugate vaccine (DTPa-HBV-IPV/Hib: Infanrix™ hexa; GlaxoSmithKline Vaccines) in the first 2 years of life through routine vaccine services in Germany. The ability of these children to mount an anamnestic response to a challenge dose of monovalent HBV vaccine (Engerix™ B Kinder; GlaxoSmithKline Vaccines) was also assessed. Before the challenge dose, 78.5% of children had anti-HBs levels ≥6.2 mIU/mL (seropositive) and 72.2% had anti-HBs levels ≥10 mIU/mL (seroprotected). Post-challenge, 98.9% had anti-HBs levels ≥10 mIU/mL and 95.8% had anti-HBs ≥100 mIU/mL. An anamnestic response to the challenge was observed in 96.6% of all subjects. The challenge dose was well tolerated, with a reactogenicity and safety profile consistent with published data. DTPa-HBV-IPV/Hib induces long-lasting immune memory to HBV that appears very similar to that induced by monovalent HBV vaccines. Protection against hepatitis B may be conferred through immune memory in subjects who responded to primary vaccination, even when they subsequently lose detectable levels of circulating anti-HBs antibodies.