Like GG2, I take D3 and zinc daily. I have been taking D3 for years, recently increased the dose to 10,000 IU/day, and haven’t been sick in a long time. YMMV of course.
I was taking 5000 IU of D and Vitamin C (1000 mg/1 Gram) every other day since “D” is fat soluble but after seeing this video, I’m going to take take both D and C daily.