Comparison of hepatitis B surface antibody levels induced by the pentavalent DTwP-HB-Hib versus the hexavalent DTaP-HB-Hib-IPV vaccine, administered to infants at 2, 4, 6, and 18 months of age, following monovalent hepatitis B vaccination at birth

Background: In Thailand, the hepatitis B (HB) vaccine is administered as a tetravalent vaccine (DTwP-HB) to all infants at 2, 4, and 6 months of age, following an initial vaccination with a monovalent HB vaccine at birth. As part of ongoing vaccine evaluation, we aimed to compare the hepatitis B immunogenicity profiles of children who had received either the pentavalent (DTwP-HB-Hib) or the hexavalent (DTaP-HB-Hib-IPV) vaccine. Methods: Two groups of infants, whose mothers previously received the tetanus-diphtheria-acellular pertussis vaccine (Tdap), were randomly vaccinated with either pentavalent or hexavalent vaccine at 2, 4, 6, and 18 months of age, following monovalent HB vaccine at birth. Blood samples were obtained at birth, one-month post-primary series immunization (mo 7), pre-booster (mo 18), one-month post-booster (mo 19), and six months post-booster (mo 24). The third group of infants, whose mothers did not receive Tdap, was vaccinated with DTwP-HB-Hib (ER pentavalent group). Levels of HBsAg, anti-HBc, and anti-HBs were evaluated by means of an automated Chemiluminescent Microparticle Immunoassay. Results: Anti-HBs levels of >= 10 mIU/ml were achieved in 99.2% (hexavalent group), 99.2% (pentavalent group), and 98.5% (ER pentavalent group) of infants, after four-dose immunization (at 0, 2, 4, 6 months of age). One month after the additional dose given at 18 months of age, anti-HBs levels of >= 10 were observed in 100% (hexavalent group), 99.2% (pentavalent group), and 93.8% (EPI pentavalent group) of infants. At 24 months of age, higher percentages of infants achieving anti-HBs levels >= 10 were found in the hexavalent group (98.3%) compared to the pentavalent group (86.5%). Conclusions: Both vaccines were effective in inducing anti-HBs levels of >= 10 mIU/ml, and therefore either can be used as a single formula booster at 18 months of age to simplify vaccine administration under the Expanded Program on Immunization in Thailand. (C) 2019 Elsevier Ltd. All rights reserved.