I recall an article a few months ago that discussed the Vitamin-D link in more depth, and a plausible mechanism was already suggested: vitamin D regulates the i

I recall an article a few months ago that discussed the Vitamin-D link in more depth, and a plausible mechanism was already suggested: vitamin D regulates the immune system response. People with low vitamin D levels are more likely to experience severe cytokine storms. PDF from April 2020: https://www.medrxiv.org/content/medrxiv/early/2020/04/10/2020.04.08.20058578.full.pdf?mod=article_inline https://www.medrxiv.org/content/medrxiv/early/2020/04/10/202... The impact of Vit D in enhancing immune response (including flu and previous coronaviruses) has widely been studied and firmly established. Vit D can also suppress cytokine storm, which may substantially increase the chances of avoiding a severe case of COVID-19