Cereda E, Bogliolo L, Klersy C, et al. - In this single-center cohort study, researchers sought to determine the prevalence of 25(OH)vitamin D deficiency in coronavirus disease 2019 (COVID-19) patients admitted to an Italian referral hospital and explore its connection with clinical results and disease severity markers. One hundred twenty-nine consecutive adult COVID-19 patients hospitalized in an Italian referral center were recruited from March to April 2020. Data reported that the prevalence of 25(OH)vitamin D insufficiency, moderate deficiency and severe deficiency was 13.2%, 22.5% and 54.3%, respectively. In the hospitalized severe COVID-19 patients, very low 25(OH)vitamin D levels were highly prevalent and indicative of deficiency, but low 25(OH)vitamin D levels were not correlated with outcome variables. Whether 25(OH)vitamin D adequacy may affect clinical outcomes in COVID-19 and the unexpected relationship between higher 25(OH)vitamin D levels and mortality need further investigations by large intervention trials.