Dr John Campbell (a PhD nurse educator) who has been putting out youtube videos of research-based plain English explanations of various aspects of the COVID-19 pandemic, has been beating this drum regularly for eight or nine months. One of his videos did mention that vitamin D deficiency is very high in Spain, particularly in some specific regions of Spain, so don't jump to conclusions about the amount of risk reduction from adequate vitamin D levels. Dr Fauci is reported to be taking 6000 units per day, way higher than the recommended daily allowance in the USA.