Letermovir vs Valganciclovir in CMV R+ Kidney Transplant

The purpose of this study is to find out whether letermovir can help prevent cytomegalovirus (CMV) infection in kidney transplant recipients who are CMV seropositive. To do this, researchers will compare patients who received letermovir with a group of historical patients who received valganciclovir ("mini dose"). Both groups will be on CMV prophylaxis drug for 90 days post-transplant. The main question the study wants to answer is: • Does letermovir work as well as valganciclovir in preventing CMV infections during the first 12 months after a kidney transplant? The study will also look at other important questions: * Is letermovir easier for patients to tolerate than valganciclovir? * How long does it take for a CMV infection to appear in each group? * Are there differences in "breakthrough" CMV infections between the two medications? * For patients who develop CMV that becomes resistant to treatment, are the resistance patterns different between the two groups