Why quantity of diphtheria and pertussis vaccines is reduced for children 7 years onwards?

The pediatric formulations usually have 3-5 times as much of the diphtheria component than what is in the adult/ adolescent formulation. Similarly, the formulations for adults/adolescents have around one third of acellular pertussis content than pediatric formulations. The amount of tetanus toxoid in each of the products remains almost equivalent. Dose reduction for diphtheria and pertussis is necessary because of the increased incidence of local and systemic reactions particularly to diphtheria toxoid and to some extent to acellular pertussis component in older children and adults [1-4].