Diphtheria Antitoxin Levels among Children Primed with a Diphtheria and Tetanus Toxoids and Acellular Pertussis Vaccine Lot with a Subpotent Diphtheria Toxoid Component

One lot of a nationally distributed diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccine was recalled in January 1999 because of a subpotent diphtheria toxoid component. To evaluate vaccine immunogenicity, children who had received the recalled lot for at least 2 of the 3 doses of their primary series were identified. Diphtheria antitoxin (DAT) levels were then prospectively assessed before and after dose 4 of (fully potent) DTaP vaccine. Of the 105 children evaluated, 84% had prevaccination DAT levels