About 706 children received immunoglobulin for Kawasaki disease in 2020/21, compared with an average of 336 children per year over the previous five years.
The causes are not fully understood, but the condition is believed to be related to the body’s immune response to infections.
Experts said the sudden increase could be the result of cases caused by Covid.
An additional 135 children also needed immunoglobulin for pediatric multisystem inflammatory syndrome, a new similar disorder associated with Covid.
Jerry Gogarty, director of drug plasma at NHS Blood and Transplant (NHSBT), said: “You can help by donating plasma or blood – you have the drug in you.”
Kawasaki disease is the leading cause of heart disease that develops after birth in children under the age of five.
This causes inflammation and swelling of the blood vessels, which can lead to heart failure and death if not treated quickly.
Symptoms include a rash, swollen glands in the neck, dry or cracked lips, a swollen or bumpy red tongue, and swollen hands and feet.
Immunoglobulin is made from infection-fighting antibodies extracted from plasma, the liquid part of the blood.
In total, about 17,000 people in England receive plasma treatment each year.
Between 1998 and 2021, there was a ban on the use of plasma from UK donors due to concerns about the spread of Creutzfeldt-Jakob disease, the human form of mad cow disease.
After relying on international supplies for decades, donations have now resurfaced as the NHS builds up an internal supply chain.
But desperately need more. NHSBT has 5,850 registered plasma donors, about half of the 10,200 needed to secure a stable supply.
Dr Jethro Herberg, an expert in pediatric infectious diseases at Imperial College London, said: “Immunoglobulin is a valuable resource as it is an essential drug for the treatment of Kawasaki disease. We absolutely need to ensure a secure supply.”
Rachel McCormack, founder of the Societi Foundation, the UK-based Kawasaki disease foundation, said: “Rapid diagnosis and prompt treatment with immunoglobulin in children with Kawasaki disease could be revolutionary in saving lives and protecting tiny hearts from the devastating effects of lifelong heart disease.
“Every year more and more children are affected by Kawasaki disease, so donating plasma means children can get the urgent treatment they need and have a much better chance of recovery.”
Health Minister Neil O’Brien said: “More plasma donors are needed to treat Kawasaki disease and we are working closely with NHS Blood and Transplant to increase supplies so we can provide the best possible patient care.
“Thanks to existing donors who have generously responded. If you can, consider donating blood or plasma – it could save someone’s life.”
Specialized plasma donation centers have been opened in Twickenham, Reading and Birmingham. Plasma can also be obtained from regular donated blood.
When donating plasma, the machine filters about 700 ml of yellow plasma from the blood in about 35 minutes.
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The blood vessels around Bella’s heart swelled as the illness took hold.
Three-year-old Bella Hessey’s life was saved by immunoglobulin treatment after she contracted Kawasaki disease as a child.
She developed symptoms, including a rash all over her body, red eyes, and a high fever, which were initially misdiagnosed as an ear and throat infection.
When the disease hit her tiny body, the blood vessels around her heart swelled.
One artery, which should have been one to two millimeters wide, swelled to 12 mm.
Bella’s mom Abigail Baker, 26, said: “The effect of the immunoglobulin was immediate. Immediately her color returned to normal.
“The next morning she started eating again and her fever was completely gone. It saved her life.”
Abigail, a recruiting consultant from Bicester, supports the call for more plasma donors.
She added: “You see comments on the Internet from people all over the world trying to get immunoglobulin because it’s expensive.
“It’s very important that people can donate again in England so that we can have a safer supply here, especially as treatment for Kawasaki disease is time-limited.”