Mr. Harrison has been widely praised and has received the Medal of the Order of Australia for his longtime support of the Australian Red Cross Blood Service and the Anti-D program.
The "man with the golden arm", as he has been dubbed, told The Sydney Morning Herald that his retirement was "a sad day" and "the end of a long run".
Mr. Harrison's blood contains a rare antibody required to make an innovative medicine called Anti-D, which protects babies from hemolytic disease, a potentially deadly condition.
Mr. Harrison had been donating blood for more than a decade when researchers found him in the 1960s and asked him to become the first donor in what would eventually come to be known as the Anti-D program. His kindness leaves a remarkable legacy, and he has put the challenge out to the Australian community to beat it.
"Saving 2 million is hard to get your head around, but if they claim that's what it is, I'm glad to have done it", Mr. Harrison told The Times.
When James was just 14 years old, he underwent major chest surgery and depended on the blood of strangers to save his life. He pledged to donate as soon as he was old enough and four years later, kept his promise. He began by donating whole blood despite an aversion to needles. James was happy to continue to donate and switch over to plasma donation in order to help as many people as possible.
Harrison was the first donor in a national Anti-D program that started in 1967. Without it, their next Rh (D) positive baby could suffer from Haemolytic Disease of the Fetusand Newborn (HDFN), which can be fatal.