Should be noted that the vitamin D levels were from the past 12 months. This is pure correlation, as Deva Boone’s excellent blog clearly explains. However, a

Should be noted that the vitamin D levels were from the past 12 months. This is pure correlation, as Deva Boone’s excellent blog clearly explains. However, a few days ago there was on the HN front page a link to what appears to be causal effect - Covid patients who were given vitamin D On admission did better than those who didn’t. That study had some limit and they had a couple of uneliminated confounders - but the body of evidence does hint that proper vitamin D supplementation is likely beneficial in fighting Covid.