Vitamin D levels are unrelated to the severity of respiratory syncytial virus bronchiolitis among hospitalized infants

Background. Vitamin D deficiency at birth has been reported as a risk factor for respiratory syncytial virus (RSV) lower respiratory tract infection during the first year of life. Limited data are available on whether an infant's vitamin D status is associated with the severity of acute RSV bronchiolitis. Methods. Infants < 1 year of age and hospitalized with their first episode of RSV bronchiolitis were enrolled into the RSV Bronchiolitis in Early Life II cohort.We investigated the relationships between vitamin D status at enrollment and the following indicators of bronchiolitis severity: duration of hospitalization, lowest oxygen saturation measured during hospitalization, and bronchiolitis severity score. Results. Among the 145 enrolled infants, the median (quartile 1 [Q1], Q3) serum 25-OH-VitD level was 36.8 (29.8, 42.3) ng/mL, with 14 infants (9.7%) having deficient serum vitamin D levels (25-OH-VitD < 20 ng/mL). Vitamin D-deficient infants were younger than infants with 25-OH-VitD ≥ 20 ng/mL (2.8 vs 4.5 months, respectively; P = .04) and were less likely to consume infant's formula (42.9% vs 87.0%, respectively; P < .01). The following indicators of acute bronchiolitis severity did not differ between infants who were vitamin D-deficient and nondeficient: duration of hospitalization (P = .53), lowest oxygen saturation (P = .45), and bronchiolitis severity score (P = .97), even after adjusting for age, and for infant's formula consumption. Conclusions. Among this cohort of infants that were hospitalized for RSV bronchiolitis, vitamin Dstatus at the time of bronchiolitis was not associated with indicators of acute bronchiolitis severity.