Long-term Follow-up of Subjects With Sickle Cell Disease Treated With Ex Vivo Gene Therapy

This is a multi-center, long-term safety and efficacy follow-up study for subjects with sickle cell disease who have been treated with ex vivo gene therapy drug product in bluebird bio-sponsored clinical studies. After completing the parent clinical study (approximately 2 years), eligible subjects will be followed for an additional 13 years for a total of 15 years post-drug product infusion. No investigational drug product will be administered in the study.