Catch ~ We kick colds, etc. very quickly in our house. We keep a canister of Ascorbic Acid (Vitamin C powder) on hand and add it to our water a couple times a day at 2250 milligrams per 1/2 tsp. When the body is sick, it will take in a LOT of vitamin C!
I am currently fighting something myself...and the vitamin C is kicking it! I had over 8,000 mg yesterday. As long as your bowels don't start to gurgle, you are at the right level for what you need. If they start to gurgle, cut back to a smaller dose.
That's what works for us anyway. I'm not a doctor.

Just an experienced mom that has read up on Vitamin C.
Vitamin C seems to help with fatigue too. Bonus!