CLINICAL AND PROGNOSTIC SIGNIFICANCE OF VITAMIN D DEFICIENCY IN CHILDREN WITH RECURRENT RESPIRATORY TRACT INFECTIONS

Vitamin D plays an essential role in immune regulation and protection against infectious diseases in childhood. In recent years, vitamin D deficiency has been increasingly recognized as a potential risk factor for recurrent respiratory tract infections. The present study aimed to evaluate the clinical and prognostic significance of vitamin D deficiency in children with recurrent respiratory tract infections. A cross-sectional observational study was conducted among children aged 1–12 years, including patients with recurrent respiratory tract infections and age-matched healthy controls. Clinical characteristics, infection frequency, hospitalization rates, and laboratory parameters were analyzed. Serum 25-hydroxyvitamin D levels were measured and classified according to international recommendations. The results demonstrated a significantly higher prevalence of vitamin D deficiency among children with recurrent respiratory tract infections compared to healthy controls. Lower serum vitamin D levels were associated with increased frequency and duration of respiratory infections, elevated inflammatory markers, and a greater risk of severe disease course. An inverse correlation was observed between vitamin D concentration and infection recurrence. The findings suggest that vitamin D deficiency represents an important modifiable risk factor in pediatric respiratory morbidity. Early detection and correction of vitamin D insufficiency may contribute to improved immune function and reduced burden of recurrent respiratory tract infections in children.