Summary
A study conducted by the University of Chicago examined the association between vitamin D levels and other clinical characteristics related to COVID-19. 489 patients were involved. Patients with a deficient vitamin D level showed a 1.77 times greater risk to test positive for COVID-19. This study showed a direct association between vitamin D deficiency and an increased risk for COVID-19 infections. More details can be found in the study.
References
Meltzer et al.