While the body will build immunity towards germs, bacteria and other invaders while you are young, you will not have complete immunity towards an INFECTION. If you don't keep a wound clean, you will get an infection. Use precautions to avoid an infection. If you have an infection, you may want to see a Doctor. An untreated infection can lead to more serious complications,even amputation.
So, NO you can not be completely Immune from infection, unless of course you are a Fruit Bat.