To give some context around the history of vitamin C research, the whole idea of megadose vitamin C as an immune system booster/cure for the common cold/cure for cancer was more or less pushed by a single figure: Linus Pauling.
He was an extremely influential and successful 20th-century chemist, who earned both a Nobel Prize in Chemistry and a Nobel Peace Prize. In his late 60s, he became interested in "orthomolecular medicine" (the theory of making people thrive through some imagined perfect balance of vitamins), and became an advocate for megadose vitamin C therapy.
He used his influence to set up some respectable large-scale trials on the subject, but when they failed to find substantial effects, Pauling basically doubled-down in his beliefs, and spent the rest of his life regarded as a minor quack.
He was an extremely influential and successful 20th-century chemist, who earned both a Nobel Prize in Chemistry and a Nobel Peace Prize. In his late 60s, he became interested in "orthomolecular medicine" (the theory of making people thrive through some imagined perfect balance of vitamins), and became an advocate for megadose vitamin C therapy.
He used his influence to set up some respectable large-scale trials on the subject, but when they failed to find substantial effects, Pauling basically doubled-down in his beliefs, and spent the rest of his life regarded as a minor quack.