+"Autumn COVID-19 surge dates in Europe correlated to latitudes, not to temperature-humidity, pointing to vitamin D as contributing factor"
+https://www.nature.com/articles/s41598-021-81419-w
+
+https://www.sciencedirect.com/science/article/pii/S0960076020302764
+https://pubmed.ncbi.nlm.nih.gov/16549493/
+
+https://vitamin-d-covid.shotwell.ca/#supplementation-studies