A group from the University of Florida etc. has found that people with vitamin D deficiency were five times more likely to be infected with COVID-19 than people without deficiency after adjusting for age groups (OR = 5.155; 95％CI、3.974–6.688; P <0.001）from a statistical study using total population of 987,849 people. Healthy diets is the base of health. Sorry for the very short blog article.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7716744/