Respiratory viral infections in children with asthma: do they matter and can we prevent them?

Ahanchian, Hamid; Jones, Carmen M; Chen, Yueh-sheng; Sly, Peter D

Vitamin D deficiency is a common worldwide problem [149] [150] . Beside importance for bone health, vitamin D plays an important role in adequate function of both the innate and adaptive immune systems including development of dendritic cells and regulatory T lymphocytes [151, 152] production of antimicrobial proteins by airway epithelium [153] , modifying the effect of intestinal flora on inflammatory disorders [107] , and modulation of the inflammatory response to viral infections [154] . Recent reports suggest that vitamin D might play a role in the recent increase in allergic disease [155] [156] [157] . Vitamin D insufficiency has been associated with a higher incidence of respiratory tract infection, wheezing illness in children [158] , reduced asthma control [159] , emergency department visits, severe asthma exacerbations and hospitalizations [70, 160] . In a recent study of 48 children from five to 18 years of age, with newly diagnosed asthma, vitamin D supplementation during the northern hemisphere winter months (September to July) prevented declining serum concentrations of 25(OH) D and reduced the risk of asthma exacerbation triggered by acute respiratory tract infections [161] .