Background:An advantage of the third-generation HBV vaccines containing preS1 and preS2 antigens was suggested by their excellent immunogenicity in humans and the rapid onset of antibody response to the S-protein of the vaccine. Sequential studies of the antibody responses to the preS1 and preS2 in relation to the anti-HBs response after immunization with preS-containing vaccines have been made in older children only.Material/Methods: Twenty-eight randomly selected, healthy newborns received either 2.5 Kg or 5 Kg of Bio-Hep-B™ (preS1, 2+S) vaccine. The children received 3 doses of vaccine according to a 0, 1, 6 months scheme. Antibodies were determined at months 6 and 9.Results: The vaccine was well tolerated and safe in newborns. Seroconversion and seroprotection were achieved in 100% of newborns after the second injection. No dose-related effect on the anti-HBs response could be observed; GMTs of anti-HBs antibodies after the 2.5 Kg and 5.0 Kg doses were 6703 and 7104 Kg IU/l, respectively. The induction of measurable levels of antibodies towards preS1- and/or preS2-antigens with 2.5 Kg and 5 Kg doses of the vaccine was noted in 29% and 50% of the newborns, respectively, at 6 and/or 9 months of vaccination. An augmented anti-HBs response was elicited in the newborns who produced anti-preS2 after vaccination with 2.5 Kg compared with 5.0 Kg of the vaccine.Conclusions: The vaccine Bio-Hep-B™ can elicit high titers of anti-HBs antibodies in newborns after only two injections. The response of newborns was directed against preS1 + preS2, or preS2 alone.

Keywords: Hepatitis B Antibodies - blood, Hepatitis B Surface Antigens - immunology, Hepatitis B Vaccines - administration & dosage, Hepatitis B Vaccines - adverse effects, Hepatitis B Vaccines - immunology, Immunization Schedule, Infant, Newborn, Protein Precursors - immunology, Hepatitis B Antibodies - blood, Hepatitis B Surface Antigens - immunology, Hepatitis B Vaccines - immunology, Immunization Schedule, Infant, Newborn, Protein Precursors - immunology