They say restoring near-normal hearing in the animals paves the way for similar treatments for people "in the near future".
Studies, published in Nature Biotechnology, corrected errors that led to the sound-sensing hairs in the ear becoming defective.
The researchers used a synthetic virus to nip in and correct the defect.
"It's unprecedented, this is the first time we've seen this level of hearing restoration," said researcher Dr Jeffrey Holt, from Boston Children's Hospital.
