Low Levels of Vitamin D Are Associated With Markers of Immuno-Inflammatory Response and Clinical Outcome in Covid-19

High prevalence of vitamin D (VD) deficiency in COVID-19 patients was reported by several studies. Since VD is a key regulating factor of both innate and adaptive immunity, it was hypothesized that VD deficiency may predispose to SARS-CoV-2 infection and lower levels of VD could be related to increased COVID-19 severity and worse outcome risks. However, to date, only few studies partially investigated the relationship between VD and inflammatory and immune response and clinical features of COVID-19 patients. The aim of this study is to evaluate the influence of vitamin D levels on COVID-19 inflammatory activity, clinical pattern and disease severity. Patients admitted to San Raffaele University Hospital for COVID-19 from February 2020 were enrolled in this study. We excluded patients with comorbidities and therapies influencing VD metabolism. 25OH-Vitamin D levels were evaluated at admission in hospital and VD insufficiency and deficiency were defined as VD level below 30 ng/mL and 20 ng/mL, respectively. A total of 88 patients were included in the study. Median (IQR) VD levels were 16.3 (11.2–23.9) ng/mL. VD insufficiency and deficiency were found in 88.6% and in 68.2% of patients, respectively. Linear regression analyses showed a positive correlation between VD levels and PaO2/FiO2 ratio (p=0.019; r=0.254), and negative correlations between VD levels and Neutrophil/Lymphocyte (N/L) ratio (p=0.04; r=-0.19), C-reactive protein (CRP) levels (p=0.047; r=-0.18) and Interleukin 6 (IL-6) levels (p=0.04; r=-0.22). Lower VD levels were found in patients affected by severe disease (needs for high-flow oxygen therapy and/or noninvasive mechanical ventilation, admitted to ICU and/or dead) than non-severe patients (13.4 ng/mL [10.37–19.15] vs 18.45 ng/mL [15.15–24.95]; p=0.007). Moreover, patients with VD deficiency had higher levels of CRP, LDH, IL-6, IFN-gamma (p=0.04, p=0.01, p=0.002, p=0.04; respectively), lower PaO2/FiO2 and higher N/L ratios (p=0.008, p=0.004; respectively), and higher rate of severe disease (65% vs 39%, p=0.02), as compared to VD non-deficient ones. In conclusion, low VD levels are widely found in hospitalized COVID-19 and may lead to increased disease severity through an excessive immune-inflammatory response. Our data suggest that reaching adequate vitamin D levels in risky population may contribute to prevention of COVID-19 occurrence and severity.