Polio may be coming back. 5 possible cases in Venezuela reported today, which would be the first in this hemisphere in over 30 years. There they are proposing polio from the live vaccines, which can happen, although very rare, or, worst, a new live strain of the virus. More likely IMHO is importation via that governments friends, as the only reservoir of it left in the wild was the Af-Pak frontier and the muslim areas of Nigeria.
As for tetanus, it always has and probably always will be around. But that might quiet some of those who want to chance it and for that herd immunity probably isn't important.