This study is exploring a new vaccine called **CMV-MVA Triplex Vaccine**. It aims to boost the body's defenses against a virus called **cytomegalovirus (CMV)**. This is important for people getting a special kind of treatment called **haploidentical hematopoietic stem cell transplant (haploHCT)**. In haploHCT, patients receive stem cells, which are special cells that can become many different types of blood cells, from a donor who is not a perfect match but is a close match. This procedure can make patients more likely to get CMV infections, which can be serious. The vaccine is being tested to see if it can help prevent these infections by making the immune system stronger. **Key Points:** - The study involves receiving the vaccine and other treatments over several months, with follow-ups up to a year. - Participants will need to undergo regular blood tests and medical visits. - The study is open to adults aged 18-75 who are planning to undergo haploHCT and meet other health criteria. Participants will be monitored closely to ensure their safety and to check how well the vaccine works.