Effect of COVID-19 Disease on Serum Vitamin D Status in Children with Asthma-A Retrospective Study.

: Vitamin D is known to decrease the risk of contracting respiratory infections and developing exacerbations for children with asthma. This research evaluates the alterations in serum vitamin D concentrations and examines lung function in children with asthma, as indicated by clinical symptoms and paraclinical results, after experiencing SARS-CoV-2 infection or other acute respiratory infections. : This retrospective study included 145 children with asthma. For each patient, the following variables were acquired: demographic data, serum vitamin D levels, GINA asthma control levels, the fraction of exhaled nitric oxide (FeNO), pulmonary function tests parameters, data related to allergies, and the presence of exacerbations. Children were divided into two groups, according to the presence or absence of SARS-CoV-2 infection or other acute respiratory infections. Variables were statistically processed in SPSS. : In total, 93 children with asthma with SARS-CoV-2 infection or other acute respiratory infections and 52 children with asthma without SARS-CoV-2 infection or other acute respiratory infections were included in the study. Median serum vitamin D values were statistically significantly lower in children with a variable airflow limitation, compared to children with normal values ( = 0.004), as well as for children with partially controlled asthma, relative to children with well controlled asthma ( < 0.0005). Similarly, children with acute respiratory infections/COVID-19 disease had lower median values of serum vitamin D, compared to children without acute respiratory infections/COVID-19 disease ( < 0.0005). A decrease in serum vitamin D value was statistically significantly associated with an increase in FeNO value for children with asthma with COVID-19 disease ( = 0.027), as well as for the entire study group ( < 0.0005). : Children with asthma who had acute respiratory infections, including COVID-19 disease, showed considerably reduced serum vitamin D levels and were linked to more significant airflow limitation, reduced asthma control and elevated airway inflammation, suggesting its potential role in influencing asthma severity and infection response.