The study evaluated the efficacy and safety of letermovir (MK-8228) for the prevention of clinically-significant CMV infection in adult, CMV-seropositive recipients of allogeneic hematopoietic stem cell transplant (HSCT). The hypothesis being tested was that MK-8228 is superior to placebo in the prevention of clinically-significant CMV infection through Week 24 post-transplant.