<<<9. Immune system
One of the actions of prednisone is to weaken the body's immune system. This effect is beneficial when treating allergies or so-called "autoimmune" diseases like arthritis, lupus, ulcerative colitis and Crohn's disease. However, whenever you weaken the immune system, you increase the body's susceptibility to infection. <<<Prednisone does not make an individual more likely to get a flu or catch a cold.>>> But, it can increase susceptibility to chickenpox (varicella) and other herpes viruses. Individuals, who have recovered from tuberculosis, or TB, can experience reactivation of the disease when on prednisone. If you have not previously had chickenpox, tell your doctor. Do not take prednisone if you have tuberculosis (active or inactive), shingles or other herpes infection of eyes, lips, or genitals. You should not be vaccinated against any infectious disease while you are on prednisone especially live polio vaccine. Allergy skin tests and TB skin tests will usually be invalid while you are on prednisone. A small number of patients on prednisone develop yeast infections of the mouth (thrush) or vagina. Fortunately, effective medications are available to combat this problem should it occur.>>>
This is a switch, me attempting to answer one of your questions. Not that I'm any kind of authority, I just searched your question and found this.
My daughter was diagnosed Feb. 19/07, (13 yrs. old at time of diagnosis), with Crohn's of the Terminal Illium. Initially, 9 weeks of Prednisone, currently taking 2000mgs of Pentasa.