Incidence rates of recurrent stroke in individuals with SCD receiving either hydroxyurea therapy, blood transfusion therapy, or no therapy for secondary stroke prevention in published studies since 1995. The expected incidence rates of stroke recurrence while on regular blood transfusion therapy, hydroxyurea therapy, or no therapy were found to be 1.9 (95% CI, 1.0-2.9), 3.8 (95% CI, 1.9-5.7), and 29.1 (95% CI, 19.2-38.9) events per 100 patient years, respectively.