I see Vit C mentioned in these recommended regimes regularly, but unfortunately people have no idea what they are talking about. Massive doses of Vit C have been shown to be helpful treating Covid however only in clinical settings where they are monitoring the amount in the bloodstream AND only when it's given intravenously. The dose at which it becomes effective is around 6 grams. But taking 6+ grams orally is probably going to give you the shits and there's no way to be sure what the level in the bloodstream will be. Vit C tabs are cheap and you aren't going to hurt yourself if you take too much -- other than potential intestinal upset -- because you'll piss most of it out anyways. But thinking that it's going to help protect against Covid is merely wishful thinking. Taking Vit D and Zinc daily, however, has been shown to be effective. And if you do start to show cold/flu symptoms then 6 times a day put a Zinc lozenges in the back of your throat and let it dissolve there.