Hasegawa K, et al. - In this prospective multicenter study of infants (age <1 year) hospitalized with bronchiolitis, researchers tried to gain insight into the relation of circulating 25-hydroxyvitamin D (25OHD) with the many downstream functional molecules in target organs – such as the airway – and with clinical outcomes. In findings, vitamin D-related airway metabolites having an association with risks of bronchiolitis severity was highlighted.