Hi there,
This problem is a difficult one. When immunosuppressant medications are used, CMV and other opportunistic infections are unfortunate (and expected) side affects. The only way to reduce their frequency is to reduce immunosuppression, but that carries the risk of rejection of the kidney. The balance required to prevent rejection but also infection is achieved through a bit of trial and error of medication dosages. Sorry I don't have a more concrete answer.
Dr. Jordan Weinstein