: Meta-analyses indicate that low vitamin D status increases the risk of ICU admission by more than twofold and the risk of death by 1.22- to 4.15-fold. In a large study, mortality among deficient patients was 25.6%, compared to just 2.3% for those with sufficient levels.
Vitamin D is believed to modulate the immune system through several pathways: Vitamin D and COVID-19: Clinical Evidence and ... - PMC Low Vitamin D Levels Tied to Odds for Severe COVID
: Patients with vitamin D deficiency were found to be up to 14 times more likely to have a severe or fatal disease course in some observational studies. : Meta-analyses indicate that low vitamin D status