Optimal Timing of Hepatitis B Vaccination After Transplants

Inclusion Criteria: 1. Patients must be ≥ 16 years old; 2. Patients receiving hematopoietic cell transplantation; 3. Patients achieving complete molecular remission; 4. Patients or their guardians have to sign an informed consent form before the start of the research procedure. Exclusion Criteria: 1. Multiple transplantations; 2. Donors' HBV-DNA or HBsAg are positive; 3. Patients' HBV-DNA or HBsAg are positive before transplantation or \< 3 months after transplantation; 4. Patients who are unable to comply with the research treatments and monitoring requirements due to mental or other medical conditions; 5. Patients who are ineligible for the study due to other reasons which would cause unacceptable risks to the patients.