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
Is a recipient of a primary or secondary allograft kidney
Is at least 4 weeks posttransplant and not more than 52 weeks posttransplant at the time of enrollment (Day 1) and is being managed per local standard of care
Has stable kidney function posttransplant
Has undetectable CMV deoxyribonucleic acid (DNA) from a plasma or whole blood sample collected within 14 days prior to enrollment
Has CMV disease or suspected CMV disease between screening and enrollment
Is on dialysis or plasmapheresis at the time of enrollment
Has evidence of CMV viremia at any time from screening until the time of enrollment
Has Child-Pugh B or C hepatic insufficiency within 14 days before enrollment