RecruitingPhase 1Drug trialA Clinical Study of Letermovir (MK-8228) in Children and Adolescents Who Receive a Kidney Transplant (KT) (MK-8228-077)Researchers are looking for a way to prevent cytomegalovirus (CMV) in children and adolescents who receive a kidney transplant (KT) and weigh less than 40 kilograms (88.2 pounds). The goals of the study are to: * Learn what happens to letermovir in the body over time * Learn about the safety of letermovir and if participants tolerate it