Abstract
Six NIH Vaccine Treatment and Evaluation Units (VTEUs) enrolled 1340 15- to 20-month-old children to receive one of 12 DTaP or a DTwP vaccine as a booster after they had received 3 primary doses of the same DTaP or a DTwP at 2, 4, and 6 months of age. Fever, irritability, and injection site redness, swelling, and pain was assessed for 3 days after vaccination. Pre- and post- sera were analyzed for antibody (Ab) to pertussis toxin (PT), filamentous hemagglutinin (FHA), fimbriae (FIM), pertactin (PRN), and diphtheria (D) and tetanus (T) toxoids. Pertussis toxin neutralization (CHO) and agglutinating antibodies (AGG) were also measured for a subset of children. Common reactions increased after the booster dose compared with the primary series for both DTaP and DTwP; however, DTaP vaccines produced fewer reactions than DTwP. Significant variation in the occurrence of reactions among DTaP groups was observed. Priming with DTaP or DTwP did not influence the rate of reactions to DTaP boosting. Significant increases in Abs directed against the included antigens were observed for all vaccines; post booster Ab titers differed among the DTaP and DTwP vaccines. For children primed and boosted with the same DTaP, Ab levels correlated poorly with the quantity of antigen included for PT, D and T toxoid; for FHA, PRN and FIM there was a closer correlation. Children primed with DTwP and boosted with DTaP had higher Ab responses to PT than children who were primed with DTaP, indicating enhanced DTwP priming. Some DTaP vaccines given as a fourth dose in DTwP primed children elicited Ab to pertussis components not reported to be in the vaccines; suggesting the probable presence of trace quantities of these components. Although the highest AGG titers were observed in children immunized with DTaP vaccines containing FIM, AGG Ab responses occurred for all vaccines containing FHA. Use of DTaP for boosters in 15- to 20-month-old children has revealed reaction rates and immunogenicity results generally consistant with those following the primary series; however moderate but measurable increases in reactogenicity and some unexpected immunogenicity results were observed. Spon: NIH/NIAID& the vaccine companies.
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