Link between Vitamin D and COVID?

Many studies have shown an association between vitamin D and Covid outcomes, but the evidence is largely observational - meaning it looks at what happens to people with higher and lower levels of vitamin D without controlling for other factors.

Observational studies do show certain groups are both more likely to have vitamin D deficiencies and to catch Covid - older people, people with obesity, people with darker skin (including black and South Asian people).
Source : BBC