One-year post-primary antibody persistence and booster immune response to a fully liquid five-component acellular pertussis, diphtheria, tetanus, inactivated poliomyelitis, Haemophilus influenzae type b conjugate vaccine

SummaryObjectiveTo evaluate antibody persistence one year after three-dose primary vaccination and booster immune response during the second year of life for a fully liquid diphtheria–tetanus–acellular pertussis–inactivated poliomyelitis–Haemophilus influenzae type b (DTaP–IPV–PRP∼T) vaccine.MethodsInfants at 18–19 months of age were given a booster dose of either DTaP–IPV–PRP∼T (group A) or DTaP–IPV plus PRP∼T at separate injection sites (group B), after primary vaccination at two, four and six months of age, with the same vaccines. Antibody concentrations were measured pre- and post-booster. Reactogenicity and safety were evaluated from parent reports.ResultsBefore the booster dose, 93.1% of group A and 95.1% of group B children still had anti-PRP antibody titers ≥0.15 μg/ml. All children had antibody levels believed to protect against tetanus, polio 1 (except one subject in group B), polio 2, polio 3, and diphtheria (except one subject in group A). At least 94% of children still had antibody concentrations ≥5 ELISA units (EU) to pertussis antigens (pertussis toxoid (PT), filamentous hemagglutinin (FHA), pertactin (PRN), fimbriae 2 and 3 (FIM2+3)). One month after the booster dose, all subjects achieved antibody concentrations or titers believed to be protective for PRP (polyribose ribitol phosphate)(≥1 μg/ml), diphtheria and tetanus (≥0.1 IU/ml) and poliovirus types 1, 2, and 3 (≥8 1/dil.), and at least 90.5% of subjects had four-fold increases in antibody concentrations to pertussis antigens following the booster. Anti-PRP geometric mean titers (GMTs) increased from 1.07 to 59.6 μg/ml and from 1.8 to 62.2 μg/ml in groups A and B, respectively. Both vaccine groups showed low reactogenicity rates.ConclusionsThe fully liquid pentavalent DTaP–IPV–PRP∼T vaccine is highly immunogenic, with good antibody persistence for each antigen approximately one year after primary vaccination and strong booster responses at 18–19 months of age. Because this combined vaccine is fully liquid, requiring no reconstitution of lyophilized PRP∼T, the ease of use and proper administration are improved.