Why this matters:  There is still a lot of work to do.  There is no direct connection between low Vitamin-D levels and COVID-19.   What does this mean for you:  Vitamin-D deficiency is quite common in certain populations, including people with dark skin, people who are homebound or in nursing homes, and obese people. Ways to quickly get Vitamin D: Fish:  Salmon and Tuna are good natural sources of Vitamin D. Supplements:  (600 to 800 international units per day). Fortified foods: Cereals, milk, & orange juice.