An investigational gene therapy can safely restore the immune systems of infants and children who have a rare, life-threatening inherited immunodeficiency disorder, according to research supported in part by the National Institutes of Health. The researchers found that 48 of 50 children who received the gene therapy retained their replenished immune system function two to three years later and did not require additional treatments for their condition, known as severe combined immunodeficiency due to adenosine deaminase deficiency, or ADA-SCID. The findings were published today in the New England Journal of Medicine.