People with severe congenital, developmental, or early-onset medical disorders that make them particularly vulnerable. This includes cerebral palsy; spina bifida; congenital heart disease; type 1 diabetes; inherited metabolic disorders; severe neurological disorders including epilepsy; severe genetic disorders including Down Syndrome, Fragile X, Prader Willi Syndrome, and Turner Syndrome; severe lung disease including cystic fibrosis and severe asthma; sickle cell anemia; and alpha and beta thalassemia.