Don't delay your child's immunizations until he is age two. Some of the diseases that we immunize children for are most dangerous to babies under two years old. Pertussis (whooping cough) is one example. A three-year-old who gets pertussis will be sick, but will most likely recover without difficulty. A five-month-old who gets pertussis may likely have severe, and sometimes fatal, symptoms.
Other important immunizations that prevent life-threatening diseases and decrease the exposure of the germs to others are the Hib (hemophilus influenza type B) and pneumococcal vaccines, both of which prevent meningitis and serious bacterial infections in young infants. Also, we still do see cases of tetanus (the T in DTP) in infants who have not been immunized.
It is easy these days to think you can wait until children are older, since we have conquered so many infections that were such a scourge 50 years ago, but those infections have not disappeared. Outbreaks still occur, and the children who are devastated by them are the ones who have not been immunized.