Edward Willis-Hall received the gene therapy drug, Zolgensma, at Sheffield Children's Hospital in England.
David Vetter, known as "bubble boy," who died in 1984, is perhaps the most famous sufferer of severe combined immunodeficiency.
"He is dying to see a real rainbow," his mother said.
Gene therapies are probably still a decade away from being used routinely to treat genetic causes of hearing loss in humans.
The price likely won't be announced until January, according to a spokesperson.
But these breakthroughs are not going to come cheap.