The purpose of this trial is to evaluate a CMV vaccine given to related donor/recipient pairs (donors prior to peripheral blood stem cell donation and CMV-seropositive recipients just before and after transplantation) and CMV-seropositive recipient-only subjects (related or unrelated) to determine incidence rates of CMV infection, disease, and other complications from immunosuppression and/or transplantation. The outcomes for the groups receiving CMV vaccine will be compared to the outcomes for the group that received the placebo vaccine to see if there is a clinical benefit. For this trial, donors and recipients must have matched HLA genotype (matched at 5/6 or 6/6 HLA loci).