Question: why is dtap used instead of dtp?
Answer: DTaP produces fewer side effects and is a safer version of an older vaccine called DTP, which is no longer used in the United States. Tdap vaccine is licensed for people 10 years through 64 years of age. Tdap contains a lower concentration of diphtheria and pertussis toxoids than DTaP. Tdap is given at 11-12 years.