https://www.sciencedirect.com/science/article/pii/S0960076020302764
https://pubmed.ncbi.nlm.nih.gov/16549493/
+https://vitamin-d-covid.shotwell.ca/#supplementation-studies
+
https://en.wikipedia.org/wiki/Scientific_racism
[racialists get annoyed that people use "skin color" as a metonym for "race", but in this case, we actually are talking about skin color!]