ABSTRACT
Background There are many studies on relationship between vitamin D and coronavirus disease 2019 (COVID-19), while the results are matters of debate and the mechanisms remain unknown. The present study to assess the impact of serum 25-hydroxyvitamin D [25(OH)D] levels on the severity of disease in hospitalized COVID-19 patients and identify potential mechanisms.Methods A total of 399 hospitalized COVID-19 patients were recruited from three centers between December 19, 2022, and February 1, 2023.Results Levels of 25(OH)D were significantly lower in the deceased group than other three groups (P < 0.05). The levels of 25(OH)D (odds ratio = 0.986, 95% confidence interval: 0.973–0.998, P = 0.024) and IL-5 (odds ratio = 1.239, 95% confidence interval: 1.104–1.391, P = 0.04) were independent risk factors for the severity of COVID-19 disease upon admission. Serum 25(OH)D levels combined with IL-5 levels and eosinophil (Eos) counts were able to predict the mortality of patients with COVID-19. Circulating 25(OH)D status correlated negatively with the expression of IL-5 (r=-0.262, P < 0.001) and was positively linked with CD8+ T cell counts (r=-0.121, P < 0.05) in patients with COVID-19.Conclusions Most COVID-19 patients have vitamin D deficiency and a severe deficiency is associated with fatal outcomes. This study found that the serum 25(OH)D status in COVID-19 patients correlated negatively with the expression of IL-5. The specific mechanism for this relationship is worth further exploration.Trial registration This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-ncnd/4.0/).