Sickle cell anemia (SCA) is among the world's most common and devastating blood disorders, affecting more than 300,000 newborns per year. Most infants with SCA are born in the low-resource settings of sub- Saharan Africa, where an estimated 50-90% will die before 5 years of age due to lack of early diagnosis and appropriate care. Hydroxyurea is a safe and effective once-daily oral medication that has become the standard of care for the treatment of children with SCA in high-resource settings. There is now a growing body of evidence to support the safety and clinical benefits of hydroxyurea for the treatment of SCA in sub-Saharan Africa. The requirement for frequent laboratory monitoring, uncertainties about appropriate, most effective dosing, and the concern for hematologic laboratory toxicities, however, will continue to limit widespread hydroxyurea utilization and real-world effectiveness. The investigators have recently developed and prospectively evaluated an individualized, pharmacokinetics-guided hydroxyurea dosing strategy for children with SCA that has demonstrated optimal clinical and laboratory benefits with minimal toxicity. In this research study, the investigators aim to extend this precision medicine approach to Africa.