Thanks for the sources. Aha, so Vitamin D (as we know it) is indeed mainly for prevention, as it usually takes a week to get the "good effects" -- so for treatment, it's HCQ, zinc, zithromicin, and CALCIFEDIOL

The reason for giving this type of vitamin D is that the usual supplement type takes about 7 days to turn into calcifediol, so by giving patients calcifediol itself, you get the good effects without having to wait 7 or so days