Long - Term Follow Up of Sickle Cell Disease and Beta-thalassemia Subjects Previously Exposed to BIVV003 or ST-400.

Primary Objectives: Long-term safety of BIVV003 in participants with severe sickle cell disease (SCD) and ST- 400 in participants with transfusion-dependent beta-thalassemia (TDT) Secondary Objectives: * Long-term efficacy of the biological treatment effect of BIVV003 in SCD * Long-term efficacy of the clinical treatment effect of BIVV003 on SCD-related clinical events * Long-term efficacy of the biological treatment effect of ST-400 in TDT * Long-term efficacy of the clinical treatment effect of ST-400 in TDT

The total study duration is up to 15 years of follow-up post BIVV003 and/or ST-400 infusion.