Children primed with DTaP vaccines have a weaker response to the pertussis component of the Tdap booster vaccine, compared with children primed with the whole-cell vaccine (DTwP), according to a study in Vaccine.
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Michael D. Decker, MD, and colleagues conducted a study in children aged 11-12 years who had been primed with DTaP (NCT01629589) that essentially mirrored one from 6 years earlier in children primed with DTwP when it was still the more commonly used vaccine (NCT00319553). This later study randomized 211 patients to Tdap5 and 212 to Tdap3, both licensed Tdap vaccines that had been used and compared in the earlier study. The only 35% as high for Tdap5 (31.0 vs. 86.7 endotoxin units/mL, respectively; 95% confidence interval, 30%-40%) and 32% as high (44.1 vs. 136 endotoxin units/mL; 95% CI, 28%-38%) for Tdap3.
The authors noted that, because studies including children primed with DTwP are usually much older, comparisons like the one made in this study can be unreliable because of various possible confounding factors – such as changes in manufacturing process, different assays used, changing characteristics in study populations or pertussis transmission, and so on – cannot be entirely excluded. However, one of the strengths of this study, they suggested, is that “all were randomized experimental studies conducted by Sanofi Pasteur using similar procedures (including time of sera collection), and sera from all were assayed by a single laboratory (GCI) employing consistent, [Food and Drug Administration]–accepted assays.”
They did note that estimates of mean pertussis antibodies was limited by sample sizes; however, they believed the results were sufficient for the comparisons in the study.
All authors of the study were employees of Sanofi Pasteur, which funded the study and also manufactures the Tdap5 vaccine.
SOURCE: Decker MD et al. Vaccine. 2019 Jul 10. doi: 10.1016/j.vaccine.2019.07.015.