Stop waiting for a miracle drug: A Boston University doctor says a sufficient amount of vitamin D can cut the risk of catching coronavirus by 54%. Dr. Michael Holick, professor of medicine, physiology and biophysics at Boston University School of Medicine, and his colleagues studied blood samples from Quest Diagnostics of more than 190,000 Americans from all 50 states and found that those who had deficient levels of vitamin D had 54% higher COVID positivity compared to those with adequate levels of vitamin D in the blood.