The Hold My Hand singer underwent an operation to remove a polyp from her vocal cords in June (15) and she spent three weeks resting her voice.
The health crisis hit just days before her single with rapper Tinie Tempah, Not Letting Go, was due for release in the U.K. and she had to drop out of promotional appearances, so the hip-hop star enlisted another singer to replace Jess for performances of the track.
However, Jess was not happy with the stand-in after catching one of their performances on TV, telling Britain's Daily Star newspaper, "I was gutted because I had to cancel all our promo together when my voice went. The hardest part was watching him perform it on TV with another vocalist, because she got the lyrics wrong. I was shouting at the screen. Well, I couldn't actually shout because of doctor's orders, but I wanted to."
Jess admits she was scared of having the surgery, adding, "It's probably one of the most terrifying things I've gone through. I basically damaged the muscles on my vocal cords and the only way to recover was to have them operated on.
"Sam Smith, who had the same thing, gave me great advice... In every operation there's a risk, whatever they say. They can never 100 per cent you're gonna be better."
The Stay With Me singer underwent a similar procedure in May (15).