Safety and immunogenicity of a diphtheria, tetanus, and acellular pertussis-inactivated poliovirus vaccine/Haemophilus influenzae type b combination vaccine administered to Taiwanese infants at 2, 4, and 6 months of age

Background: Combined vaccines are urgently needed to ensure compliance with the increasing number of recommended vaccines for children. We evaluated the safety and antibody response to a diphtheria, tetanus, and acellular pertussis-inactivated poliovirus vaccine/Haemophilus influenzae type b (DTaP-IPV/Hib) combination vaccine administrated to infants at 2, 4, and 6 months of age. Methods: Sixty healthy infants between 6 and 12 weeks of age were enrolled. One group of vaccines received the DTaP-IPV/Hib in a single injection, while another group concurrently received DTaP-IPV and Hib at separate injection sites. Solicited adverse events were monitored by parental observation and were recorded on a diary card. Levels of serum antibodies to DTaP and polyribosyl-ribitolphosphate-tetanus (PRP-T) antigens were collected before the first vaccine dose and 1 month after the third vaccine dose. Results: The combined-injection group tended to have lower local reactions, and there was no increase in reactogenicity when compared with the separate-injection group. Seroconversion rates were 100% in both groups for all antigens, except for the anti-polio 2 antibody in the combined-injection group (96.4%). The combined-injection group had lower antibody levels of PRP (8.45 μg/ml) than did the separate-injection group (20.61 μg/ml). However, the percentage of vaccines achieving protective levels of antibody to PRP (≥ 0.15 μg/ml or ≥ 1.0 μg/ml) was similar in both groups. Conclusions: DTaP-IPV/Hib may be safely and effectively administered to healthy infants, using a 2-, 4-, and 6-month vaccination schedule. This combined vaccine is cost-effective, more acceptable to parents and physicians, and minimizes distress to infants.