Vitamin D and immunity

Vit D
https://news.harvard.edu/gazette/story/2017/02/study-confirms-vitamin-d-protects-against-cold-and-flu/

https://www.bmj.com/content/356/bmj.i6583

https://cks.nice.org.uk/vitamin-d-deficiency-in-adults-treatment-and-prevention#!scenario:1