Recurrent respiratory diseases in children remain a major challenge in pediatric healthcare due to their high prevalence, tendency to relapse, and potential to negatively affect physical development and immune function. Frequent episodes of respiratory infections during childhood may lead to chronic inflammation of the airways, increased susceptibility to further infections, and a decline in overall quality of life. In recent years, growing attention has been directed toward vitamin D as a key factor influencing immune regulation and respiratory health in children.

Vitamin D plays an essential role in both innate and adaptive immune responses. It exhibits immunomodulatory, anti-inflammatory, and antimicrobial properties that contribute to the protection of the respiratory tract. Vitamin D deficiency is widespread among children, particularly in regions with limited sunlight exposure and inadequate dietary intake, and has been strongly associated with an increased risk of recurrent respiratory infections, prolonged disease duration, and more severe clinical manifestations.

The aim of this study is to analyze the specific features of the role of vitamin D in children with recurrent respiratory diseases, with a focus on its influence on infection frequency, severity, and recovery outcomes. Understanding the immunological and clinical significance of vitamin D may support the development of effective preventive and therapeutic strategies, ultimately reducing the burden of recurrent respiratory diseases in pediatric populations.