Reactogenicity and Immunogenicity at Preschool Age of a Booster Dose of Two Three-Component Diphtheria-Tetanus-Acellular Pertussis Vaccines in Children Primed in Infancy With Acellular Vaccines

Objectives.To determine the reactogenicity and immunogenicity of a fourth dose of 2 three-component acellular pertussis vaccines combined with diphtheria-tetanus-acellular pertussis (DTaP) when administered at preschool age to children primed in infancy with 3 doses of the same DTaP and who had received a diphtheria-tetanus (DT) dose at the age of 12 months.Setting.Local health units of 4 Italian regions.Study Design.Three thousand five hundred twenty-two children, who had been randomized in the first year of life to be immunized with a DTaP vaccine by either SmithKline Beecham or Chiron Biocine, were offered a booster of the same vaccine or, if refusing, a DT vaccine at the age of 5 to 6 y…