Vitamin D and COVID-19: comparative analysis with other respiratory infections and impact of comorbidities

The COVID-19 pandemic has promoted an intensive investigation into the pathophysiological mechanisms of SARS-CoV-2 infection, risk factors, and its impact on disease severity. Vitamin D has generated significant attention for its potential role in viral prevention and immune defense due to its pleiotropic functions, including immunomodulation and antimicrobial effects. This study aimed to assess serum 25(OH)D3 levels in patients with COVID-19 compared to those with other viral respiratory infections and to evaluate associations of vitamin D levels with symptomatology, clinical characteristics, presence of comorbidities and laboratory investigation.

The study included 78 patients admitted to a hospital with COVID-19 (52 patients) or other viral respiratory infections (26 patients). Routine blood biomarkers, markers of inflammation, markers of endothelial dysfunction, serum 25(OH)D3 were analyzed, and patients were classified according to vitamin D levels and presence of comorbidities.

Most patients had vitamin D levels <30 ng/mL and there was no significant difference in 25(OH)D3 levels between patients with and without COVID-19 (p=0.768). Aging and comorbidity prevalence were significantly increased in the COVID-19 than in the non-COVID-19 group (p<0.001; p=0.049). A significant positive correlation was determined between endocan level and serum ferritin concentration in patients with COVID-19 and vitamin D deficiency. A borderline significantly elevated NLR was observed in patients with COVID-19 who were also vitamin D deficient, compared with the similar non-COVID-19 subgroup (p=0.05). In patients with COVID-19 and insufficient vitamin D, levels of 25(OH)D negatively correlated with endocan. Interestingly, COVID-19 patients with diabetes exhibited significantly lower 25(OH)D3 levels compared to non-diabetic patients (p=0.003), along with higher ferritin levels, suggesting a potential association between vitamin D deficiency and diabetes in COVID-19.

These findings contribute to the understanding of the complex interplay between vitamin D status, comorbidities, and COVID-19 outcomes, emphasizing the need for further research to elucidate their underlying mechanisms and clinical implications.