WASHINGTON, United States (AFP) -- US health officials on Thursday greenlit a first-of-its-kind gene therapy to treat a rare form of hereditary hearing loss, a breakthrough which could pave the way for other such hearing impairment treatments.

Two to three of every 1,000 children in the US are born with a hearing impairment, and it is estimated that more than half of these cases of early-onset hearing loss are caused by genetic mutations.

Developed by the American biotechnology company Regeneron, the treatment known as Otarmeni targets a rare form of hearing loss which affects around 50 newborns a year in the US.

It will be available for children and adults with severe-to-profound hearing loss caused by certain mutations in the OTOF gene, which encodes a protein critical for transmitting auditory signals from the inner ear to the brain.

While gene therapies are generally extremely expensive — particularly in the US, where they can cost several million dollars per patient — Regeneron said it intends to offer this treatment free of charge to eligible American patients.

Administered as a single injection into the ear by a surgeon, the treatment has been hailed as revolutionary by parents of affected children.

“It’s absolutely incredible,” said an emotional Sierra Smith, the young mother of Travis, a baby boy who received the treatment.

“He didn’t know his name. He couldn’t hear me tell him how much I love him. And now with Regeneron and this amazing surgery, he can listen to music, and he loves it, and he loves to dance, and he loves instruments,” Smith said at a White House event celebrating a deal signed between the pharmaceutical company and the government on the price of its other treatments.

The clinical trial, in which 20 pediatric patients aged 10 months to 16 years were evaluated, at least 80 percent experienced a significant improvement in hearing after a few months.

The US Food and Drug Administration’s accelerated approval of this treatment “signals a new era in the treatment of genetic forms of hearing loss, where reinstating 24/7 natural hearing is now possible,” said Eliot Shearer, a doctor involved in the trial.

“I’ve witnessed firsthand my trial participant responding to their mother’s voice,” said Shearer, a ear, nose and throat doctor at Boston Children’s Hospital.