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.

OBJECTIVE

To 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 approximately T) vaccine.

METHODS

Infants at 18-19 months of age were given a booster dose of either DTaP-IPV-PRP approximately T (group A) or DTaP-IPV plus PRP approximately 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.

RESULTS

Before the booster dose, 93.1% of group A and 95.1% of group B children still had anti-PRP antibody titers > or =0.15 microg/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 > or =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)(> or =1 microg/ml), diphtheria and tetanus (> or =0.1 IU/ml) and poliovirus types 1, 2, and 3 (> or =81/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 microg/ml and from 1.8 to 62.2 microg/ml in groups A and B, respectively. Both vaccine groups showed low reactogenicity rates.

CONCLUSIONS

The fully liquid pentavalent DTaP-IPV-PRP approximately 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 approximately T, the ease of use and proper administration are improved.