Campaigners are "euphoric" that NHS bosses have decided not to end lifesaving children's heart surgery at a hospital.
The decision follows a long campaign by parents of children treated at Leicester's Glenfield Hospital, charity Heart Link, MPs and hospital staff.
If plans had gone ahead, East Midlands patients would have been treated at other centres further away.
Gill Smart from Heart Link said it was "the best Christmas present ever".
"Without the people behind us we wouldn't have been able to get this result," she said.
"I would like to thank everyone who has taken the time out to go on the marches and everything, because without their help we wouldn't have achieved this outcome.
"It's the best Christmas present ever, for the children now and the children of the future."
Adam Tansey's son Albert was treated at Glenfield after being born with half of his heart missing.
Mr Tansey said the threat to Glenfield was "devastating" because "you know that your child is alive because of the individuals there".
"I don't think people can appreciate what this will mean to the parents [of the children] that are treated there," he said.
"They are incredibly worried all the time about their child's health, never mind where they are going to be treated.
"We've seen you can have treatment elsewhere but the pressure it puts on a family is just unbelievable."
- NHS England had threatened to decommission heart surgery at the East Midlands Congenital Heart Centre (EMCHC), which is located at Glenfield Hospital.
- It was part of a process to reorganise congenital heart services in England, which are for people born with heart problems, such as holes in the heart.
- Units providing specialist care for these heart problems had been under threat of closure because they were not meeting new NHS standards.
- After a public consultation, NHS England bosses said they had changed their minds but their decision was conditional on the hospital achieving "full compliance with the standards".
John Adler, chief executive of Leicester's Hospitals, said the mood inside Glenfield was "totally euphoric".
"I'm in the same mindset as everybody here. I'm totally over the moon," he said.
"The future of the unit is secure in a way it hasn't been for 10 or 15 years.
"The future is now in our hands and this decision means that the clinical team can now focus on building a world-class congenital heart service for people across the East Midlands and beyond."
Leicester West MP Liz Kendall said the future of children's heart surgery at Glenfield was the most important issue she had been involved with since being elected seven years ago.
"Today's decision by NHS England is a vindication of the hard work of our amazing doctors and nurses, and a vote of confidence in the hospital's plans for the future," she said.
"The challenge now is to keep improving services and treat even more children, with even better standards of care.
"I know that's what everyone at Glenfield is determined to do and I'll be holding NHS England and the Department of Health to account for working with us to achieve our goals."