New research from Trinity College and University of Edinburgh has examined the association between vitamin D and COVID-19, and found that ambient ultraviolet B (UVB) radiation (which is key for vitamin D production in the skin) at an individual's place of residence in the weeks before COVID-19 infection, was strongly protective against severe disease and death. Previous studies have linked vitamin D deficiency with an increased susceptibility to viral and bacterial respiratory infections. Similarly, several observational studies found a strong correlation between vitamin D deficiency and COVID-19. To overcome this, researchers were able to calculate "genetically-predicted" vitamin D level, that...