To date, we only have preliminary observations regarding the association of vitamin D deficiency and frequency and severity of COVID-19; the above mentioned study from Ilie and colleagues found a correlation between mean vitamin D levels in each country and COVID-19 cases and deaths [181]; D’Avolio and colleagues investigated vitamin D concentrations in a small cohort of 107 patients with a positive naso-pharyngeal swab for SARS-CoV2 in Switzerland, and found significantly lower vitamin D levels in patients than in controls with negative swabs [187]; Lau et al. described a high frequency of vitamin D insufficiency (84.6%) in COVID-19 patients admitted to ICU in New Orleans, with a 100% frequency in patients younger than 75 years [188].