A Low-Interventional Study of an Electronic Sickle Cell Disease Patient Reported Outcomes in Sickle Cell Participants

Inclusion Criteria - Control Group 1. Have experienced ≥1 episode(s) of MU VOC requiring documented unplanned medical intervention (eg, clinic, physician's office, emergency room or admission) requiring opioid or IV non-steroidal anti-inflammatory drug treatment within 12 months prior to Screening. 2. Participant has no history of past treatment with HU unless the reason for discontinuation was pregnancy (or pregnancy of a partner). 3. Data available for number of MU VOC(s) during the 12-month interval prior to Screening and a value for %HbF collected subsequent to 1 year of age in the absence of recent transfusion. Inclusion Criteria - HU Treatment Group 1. Have experienced ≥1 episode(s) of MU VOC requiring documented unplanned medical intervention (eg, clinic, physician's office, emergency room or admission) requiring opioid or IV non-steroidal anti-inflammatory drug treatment within12 months prior to initiation of HU. 2. Must be on a stable dose of HU ≥8 weeks prior to Day 1 with the intent of remaining on the same dose throughout the study, unless adjustments are medically necessary due to bone marrow suppression, in accordance with published guidelines. 3. Data available for number of MU VOC(s) during the 12-month interval prior to initiation of HU treatment and a value for %HbF collected subsequent to 1 year of age, prior to initiation of HU treatment and in the absence of recent transfusion. Exclusion Criteria: Medical Conditions: 1. Evidence or history of clinically significant hematological (non-SCD), renal, endocrine, pulmonary, gastrointestinal, cardiovascular (including overt stroke but excluding silent cerebral infarct), hepatic (excluding cholelithiasis), psychiatric or neurological disease as assessed from medical records. 2. Participants with any of the following acute or chronic infections or infection history as self-reported and/or assessed from medical records: * Fever ≤7 days of Screening; * Any infection requiring treatment with anti-infective drug(s) ≤2 weeks ofScreening; * COVID-19 infection unless 10 days have elapsed since symptoms first appeared, participant is without symptoms for ≥24 hours and is not experiencing post-COVID-19 symptoms. 3. Marked bone marrow suppression as evidenced by any of the following as per medical record: severe anemia, neutropenia (ANC \<1500 mm3WBC), thrombocytopenia (platelet count \<100,000 mm3) ≤8 weeks of Day 1. 4. Major surgery \<3 months prior to Day 1 as self-reported and/or assessed from medical records or planned significant medical procedures during the study. 5. Females who are pregnant or plan to become pregnant during the study. 6. Other medical or psychiatric condition including cognitive impairment that prevents accurate reporting of pain and/or assessment of SCD symptoms, recent (within the past year) or active suicidal ideation/behavior, or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study. Prior/Concomitant Therapy: 7. History of hematopoietic stem cell transplant or treatment with gene therapy as assessed from medical records. 8. History of simple transfusion ≤4 weeks of Day 1 as assessed from medical records.Prior/Concurrent Clinical Study Experience: 9. Previous administration with an investigational drug within 30days (or as determined by the local requirement) or 5half-lives preceding Day 1 (whichever is longer). Other Exclusions: 10. Active use of illicit drug as determined by the investigator. * A history or use of opioids will not be considered an exclusion if participant takes prescribed opioids for pain related to the underlying SCD. * A history or use of cannabinoids is not exclusionary. 11. History of alcohol abuse, dependence, or binge drinking within 6months of Screening as determined by the investigator. \- Binge drinking is defined as a pattern of 5 (male)and 4 (female) or more alcoholic drinks in about 2 hours. As a general rule, alcohol intake should not exceed 14 units per week (1unit = 8 ounces (240 mL) beer, 1 ounce (30mL) of 40% spirit or 3 ounces (90 mL) of wine). 12. Unwilling or unable to comply with the criteria in the Lifestyle Considerations section (Section 5.3) of this protocol. 13. Investigator site staff or Pfizer employees directly involved in the conduct of the study, site staff otherwise supervised by the investigator, and their respective family members. Lifestyle Considerations: Investigational drugs are not permitted during the study.