Hi ps1236,
Where did the 15% estimate come from? I don't think anyone can actually give you a percentage chance on whether or not hydroxyurea will work. One might make an educated guess based on the fetal hemoglobin level of the child, but even there, other factors may work for or against the success of hydroxyurea.
It may be worthwhile to try more wheatgrass, as it is perfectly safe. Folic acid, B complex, magnesium and natural vitamin E may also have some positive effect on the Hb level by helping to produce better quality red blood cells that survive longer. If you do choose to try hydroxyurea, please continue the wheatgrass also, as hydroxyurea has been shown to work in tandem with other Hb inducers. Also, add L-carnitine to the mix if hydroxyurea is started.
And yes, doctors are doing bone marrow transplants on intermedias if severe enough. Recent reports on using cord blood rather than bone marrow or harvested stem cells, show that cord blood transplants can be very successful for curing thalassemia.