The first child treated with this gene therapy is 26 and still using it as proof

Rhys Evans, the first child to receive an experimental gene therapy for X-linked severe combined immunodeficiency, is 26 and working as stage crew at Butlin's in Minehead. BBC Wales reported on November 6, 2026, that he was born in Nelson, in Caerphilly county, without a functioning immune system and spent most of his first year in a filtered room. In 2001 his parents agreed to a trial at Great Ormond Street Hospital led by Professor Adrian Thrasher of University College London.

The treatment took about 100 millilitres of his bone marrow, put a corrected gene into it, and returned the cells. Thrasher said they then waited. Within weeks an immune system began to develop. Shortly after Evans turned two he caught flu and recovered, which the family took as a test that the cells were working. Thrasher said more than 130 people have received the therapy since 2001. Great Ormond Street says most patients in its gene-therapy trials for this kind of immune failure, and some children with other conditions, have gone on to active lives. That is the hospital's summary of its trials, not a result for every diagnosis.

Evans told the BBC he has lived an ordinary life of school, university, and work, and that he has gotten through Covid twice. The limits are part of the story. He still has an antibiotic infusion once a week, and warts on his hands. The news is one patient's 25-year follow-up and a count of people treated after him. It is not a guarantee that every child with the same condition will have the same course.