Despite once being quoted as saying that he had no plans to stop donating blood, Harrison made his 1,173rd - and last - donation on Friday, at a point where he had already exceeded Australia's age limit for blood donors.
Harrison's blood has unique, disease-fighting antibodies that have been used to develop an injection called Anti-D, which helps fight against rhesus disease.
More than 3 million doses of Anti-D containing James' blood have been issued to Aussie mothers with a negative blood type since 1967.
After a few years of donating, doctors were shocked to find that his blood contained an antibody that directly neutralizes rhesus disease: a risky condition in which a pregnant woman's blood attacks her unborn child. "In Australia, up until about 1967, there were thousands of babies dying each year, doctors didn't know why", Jemma Falkenmire, of the Australian Red Cross Blood Service, told CNN in 2015.
Blood donations saved his life, so he pledged to become a blood donor. Australia became the first country in the world to be self-sufficient in the supply of Anti-D. In acute cases, the disease can lead to brain damage or even death for the unborn babies.
The discovery of Harrison's antibodies was an absolute game changer, Australian officials said.
It only happens when the mother has rhesus-negative blood (RhD negative) and the baby in her womb has rhesus-positive blood (RhD positive). Harrison discovered his blood had unique properties when he had a lung removed, aged 14.
One of the countless mothers he has helped over the decades is Joy Barnes, who works at the Red Cross Blood Bank in Sydney.
If she is pregnant with an RhD-positive baby, the antibodies can cross the placenta, causing rhesus disease in the unborn baby.
Her blood can then cross the placenta and attack the baby's blood cells, thus causing the baby to have a shortage of blood.
Harrison's naturally produced Rh+ antibodies can be used to intercept the baby's Rh+ blood cells from ever coming into contact with the mother's blood. They realized they could administer Anti-D to mothers and save the babies.
It is uncommon these days because it can usually be prevented using injections of anti-D immunoglobulin.