<qa>  What is the estimated time on study treatment?This study will determine the relative efficacy and safety of up to 100 days Valcyte prophylaxis relative to up to 200 days Valcyte prophylaxis when given for the prevention of CMV disease in high-risk DR- kidney allograft recipients. The anticipated time on study treatment is 3-12 months and the target sample size is 100-500 individuals. 