Actually the opposite.
Even if the vaxes work, they don't last forever. If you give the vax, he will never develop natural immunity, and will be at risk as an adult. If you don't give the vax there is a chance he can develop natural immunity that will protect him for life.
You can always vaccinate later. If your son does not develop natural immunity he can always choose to get the vax as an adult.
FWIW, I have never had, and have no immunity, to CP.
Wife to DH (06/10) and Mummy to DD (07/08).