Several recent studies have looked at the impact of vitamin D and zinc on COVID-19. One study of 489 people found that those who had a vitamin D deficiency were more likely to test positive for the virus. The most notable, President Trump, received a mixture of vitamin D and zinc along with a number of other experimental drugs. Ask your doctor for a blood test to determine how much vitamin D you may need with an over-the-counter pill. Vitamin D deficiency is particularly common among Hispanic and black people, two groups who have been disproportionately affected by COVID-19, according to the Mayo Clinic.