> The overall prevalence rate of vitamin D deficiency was 41.6%, with the highest rate seen in blacks (82.1%), followed by Hispanics (69.2%).

So doesn't explain the whole observed effect

Edit: also the study was in Spain, not USA

Interesting point. I wonder if this is part of the disproportionately high impact of COVID on Black in the US.

*Black people. Didn't spot my typo until after the edit event horizon, but it seemed like an important correction to make.

From the study:

> Vitamin D deficiency was found in 82.2% of COVID-19 cases and 47.2% of population-based controls (p<0.0001).

What do you think "population-based controls" means?

It means the control group: those not hospitalized with covid 19. This is a distinct idea from controlling for confounding factors.

They may have done that too for all relevant factors but we’d need to read the paper.

Then read the paper.

Covid-19 patient data is not population based.

"population based" means that the control population is adjusted to match the experiment population.

In other words, you could read the line as "Vitamin D deficiency was found in 82.2% of COVID-19 cases and 47.2% of controls, when accounting for age (p<0.0001)."