I've been taking 4 grams of C, 4000 I.U. of D and 2 grams of olive leaf extract during this past pandemic year. I also take 500 mg of magnesium to help with D absorption. Before the pandemic I took about half of this unless I felt something coming on. Olive leaf is a potent anti-viral.The moment I start feeling sick, I take one gram of vitamin C per hour, with a 3 or 4 gram dose before going to bed. Have not been sick longer than a day in probably 20 years. The late Linus Pauling recommended this for colds. Pauling was a two time Nobel prize winner and seriously smart.