A new campaign has been launched to increase awareness of the upcoming change to organ donation law.
The opt-out system, which will come into force in England from spring 2020, will mean adults are presumed to be organ donors unless they have recorded their decision not to be.
Families will still be involved before organ donation goes ahead.
A survey of more than 2,000 people by NHS Blood and Transplant, carried out in January, found only 37% of over-16s in England are aware that the law is changing.
Half (50%) of over-55s knew about the new opt-out system, but one in five (21%) 16 to 20-year-olds and 27% of people from a black, Asian and minority ethnic background did not.
The “Pass it on” campaign, which will run in the lead-up to the law change, features people releasing organ-shaped balloons, which are then given to another individual.
Anthony Clarkson, director of organ donation and transplantation for NHS Blood and Transplant, said: “Organ donation is, and always will be, a precious gift.
“Although the law is changing it will still be the generosity of individual donors and their families who decide at the most difficult time to support organ donation, which will ensure more transplants can happen and more lives can be saved.
“We want everyone to know the law around organ donation is changing, to understand how it is changing and the choices available to them.
“We want them to make their organ donation decision and to share that decision with their family.”
The law change, known as Max and Keira’s Law after a boy who received a heart transplant and a girl who donated it, replaces the current opt-in scheme.
Some groups will be excluded from the system, including under-18s, people who lack the capacity to understand the law change and people who have lived in England for less than 12 months.
Jackie Doyle-Price, Minister for Inequalities, said: “Far too many people in need of an organ transplant are still dying on a waiting list.
“We hope that Max and Keira’s Law will save hundreds of lives when it comes into effect next year – but until then, it’s vital people understand what the new law means for them.
“I want to reassure everyone that choosing to give the gift of life still is and always will remain a personal decision.
“I strongly urge people to talk to their loved ones about their wishes and make their decision clear on the register.”