Although the D and the T diseases are virtually unheard of in infants and young children in the United States, the P disease, pertussis, is still very common and can be very serious for infants.
Wouldn’t it be nice if you could just give your baby a pertussis vaccine, and delay the D and the T components until later in childhood? According to the vaccine product insert, it may be the Tetanus component of the vaccine that is responsible for some of the neurologic reactions (see The Vaccine Book), although the pertussis component is also known for this. Unfortunately, an individual pertussis vaccine isn’t available. Interestingly, the P component of this vaccine is manufactured separately from the D and T parts, then combined at the end of the process. So it seems plausible that a separate pertussis vaccine could be done. But as of now there are now such plans.