Both the prevention and cure is vitamin ‘C’, 3 to 10 grams a day depending on health and age to prevent. Ten to 50 grams a day to cure.
My self, I take from 8 to 16 grams a day I am 83, no colds, flu, drugs ever. No diseases or ills or doctor ever. Only injuries I healed except for cast and smashing off part of a finger. Never infections except bad teeth.