"Patients with vitamin D deficiency (<20 ng/mL) were 14 times more likely to have severe or critical [Covid] disease than patients with 25(OH)D ≥40 ng/mL."
Peer-reviewed study: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0263069
Just sharing my own experience here….I think that taking vitamin D3 recently caused me to get sick. It was mild. I recovered quickly. In a nutshell, I think the D3 supplements were a mild toxin in my body. I’ve since stopped the D3 and I now take a low dose of zinc (once every two to three days). Seems like my body responds better to the zinc supplement.
For now, I’m going to stick with sunlight for D. Anyone else experience something like this?