Yes, acute disease rates have gone down - ie. A form that is always stimulating the immune system as it has no way to leave the body. B. Disease rates, for the most part, were already on the decline before the vaccines came about - the trend was declining disease rates. The vaccine companies have taken credit for the continued decline, but they already were declining. What is more significant to look at are the death rates statistics from the disease.
Disease rates decrease with better sanitation, nutrition, water supplies, etc.
C. A vaccines, by giving a chronic case of the disease, only lasts about 10 years at the max. Then the person needs to be revaccinated continuing the chronic disease so they won't get the acute form of the disease. If they aren't revaccinated, or of the vaccine doesn't do the above, the person gets the disease at an age that is not normal for that disease - when it is much more severe. It just shifts the age group. Again, the vaccines here given a chronic case of the disease preventing an acute case.