Observational Clinical Study of Letermovir for Preventing CMV Infection After Allo-HSCT
The goal of this observational study is to get a series of clinical data related to the prevention of CMV infection after allo-HSCT with letemovir. The main question it aims to answer are:

Efficacy and safety of letemovir for the prevention of CMV infection after allo-HSCT.
Optimal initiation of letemovir to prevent CMV infection. Participants will be categorized into high-risk and intermediate-risk groups based on risk factors for CMV infection.Initiate letemovir prophylaxis on day +1 in high-risk patients and on days +7 to +14 in non-high-risk patients.(240 mg, qd in patients with concomitant cyclosporine; 480 mg, qd in patients with concomitant tacrolimus) to +100 days. For patients with comorbid GVHD who require intensive immunosuppression, consider extending the regimen to +200 days.Treatments they will be given and use bullets.
- EligibilityCriteria: Inclusion Criteria:  Biological age not less than 14 years. Positive CMV serology. No detectable CMV-DNA from plasma samples taken 5 days prior to randomization into groups.  Exclusion Criteria:  severe hepatic impairment; estimated creatinine clearance of less than 10 ml/min; current or recent recipients of antiviral medications with anti-CMV activity; and any other factor that affects the impact of obtaining data. - HealthyVolunteers: No - Gender: All - MinimumAge: 14 Years - MaximumAge: 100 Years - StdAgeList: Child, Adult, Older Adult - StudyPopulation: Patients who underwent hematopoietic stem cell transplantation at the Department of Hematology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, China - SamplingMethod: Non-Probability Sample