Children with ‘bubble boy disease’ who undergo gene therapy have fewer infections and hospitalizations than those receiving stem cells from a partially matched donor, new research suggests. Children with SCID-X1 are born with a genetic defect that prevents them from developing a normal immune system. Because they are prone to life-threatening infections, infants with SCID-X1 must be kept in a sterile, protective bubble and require extensive treatment for survival beyond infancy.