An adolescent–adult formulation tetanus and diptheria toxoids adsorbed combined with acellular pertussis vaccine has comparable immunogenicity but less reactogenicity in children 4–6 years of age than a pediatric formulation acellular pertussis vaccine an

In Canada, the fifth dose of the routine childhood immunization schedule against diphtheria, tetanus, pertussis and polio is given at 4–6 years of age. Up to 30% of children may have significant local reactions (redness, swelling) and this may be related to pertussis and diphtheria antigen content. We sought to determine if a combination product with lower content of pertussis and diphtheria toxoids (dTap) would result in fewer local reactions and not have inferior immunogenicity to a combination vaccine with higher pertussis and diphtheria content (diphtheria–tetanus–acellular pertussis-inactivated polio virus, DTaP-IPV). Healthy children aged 4–6 years with complete primary immunization series and a fourth dose of diphtheria and tetanus toxoids component pertussis inactivated polio and Haemophilus influenzae type B conjugate vaccine were randomized to one dose of dTap, followed in 4–6 weeks by one dose of IPV or control DTaP-IPV. Immediate reactions within 30 min, solicited injection site and systemic reactions within 14 days, and unsolicited adverse events (AE) within 6 weeks post-vaccination were monitored. Serum was collected prior to immunization, and 4–6 weeks after vaccine for diphtheria, tetanus and pertussis antibodies (Ab). Sample size was designed to detect ≥10% difference in injection site erythema, pain or swelling between groups 593 children at eight Canadian sites completed the study; no participant withdrew because of an AE. All safety endpoints on days 0–14 were less frequent in children randomized to the dTap than DTaP-IPV group: erythema (34.6% versus 51.7%), swelling (24.2% versus 33.8%) and pain (39.6% versus 67.2%). Fever was also less common (8.72% versus 16.9%). All children in both study groups had seroprotective Ab levels to diphtheria and tetanus at 4–6 weeks (≥0.10 IU/mL). The majority of children in each vaccine arm had a four-fold increase in pertussis antibodies. Fever and injection site reactions are less common in 4–6 year-old-children who receive a dTap vaccine compared to DTaP-IPV, without inferior immunogenicity.