the effect of vitamin D, magnesium, and vitamin B12 in combination on progression to severe outcomes

patients were administered 1000 IU/d oral vitamin D3, 150 mg/d oral magnesium, and 500 mcg/d oral vitamin B12.

Conclusions
A vitamin D / magnesium / vitamin B12 combination in older COVID-19 patients
was associated with a significant reduction in the proportion of patients with clinical deterioration
requiring oxygen support, intensive care support, or both.