2332. Low Serum Vitamin D Levels Are Related to Life-Threatening Respiratory Syncytial Virus Infection in Previously Healthy Infants

BACKGROUND: Serum 25-hydroxy-vitamin D (VD) effects on lung growth and immune system modulation might affect respiratory infections outcomes. Data are controversial regarding the role of VD status in the severity of Respiratory Syncytial Virus (RSV) infection. The aim of this study was to assess serum VD levels and its association with life-threatening disease (LTD) in previously healthy infants infected with RSV. METHODS: Prospective cohort study including previously healthy infants <12 months, hospitalized with a first RSV infection in 2017–2018. Viral load (VL) was assessed by qRT–PCR in nasopharyngeal aspirates and serum VD levels measured by ECLIA, in samples obtained on admission. VD deficiency was defined as levels <20 ng/mL, VD insufficiency 20–29 ng/mL, and LTD as need of intensive care and mechanical or noninvasive ventilation RESULTS: 98 patients, mean age 4.5 months (±3.1), 55 (56.1%) male. VD status: 18 (18.4%) with deficiency, 32 (32.6%) with insufficiency; 14 (77.8%) patients with deficiency had not received VD supplementation. There was no relationship between VD deficiency and anemia (P = 0.28) or age (P = 0.27). LTD was observed in 17 infants, with no significant differences in socioeconomic, pregnancy and infant variables compared with other RSV cases. Patients with LTD had significantly lower levels of VD (17.5 ng/mL [IQR 15.2–26.3] vs. 31.8 ng/mL [IQR 23.5–52.1, P < 0.001)], Figure 1. 15 patients, 88.2% of all infants with VD levels ≤29 ng/mL developed LTD compared with a study population frequency of LTD of 17.3%. Multivariable regression analysis including breastfeeding confirmed VD deficiency as a risk factor for LTD (aOR 14.3, 95% CI 3.9–51.5, P < 0.001). Normal VD values conferred protection (aOR 0.1, 95% CI 0.02–0.49, P = 0.004). VD levels inversely correlated with days of hypoxemia (P = 0.007); VD deficiency increased the risk of requiring O(2) supplementation >7 days (aOR 8.5, P < 0.001). VL did not correlate with VD levels (P = 0.696), length of stay (P = 0.378), days of hypoxemia (P = 0.681). VL was not associated with LTD (P = 0.42). CONCLUSION: Vitamin D deficiency was a risk factor for LTD in previously healthy infants with RSV infection. Viral titers did not correlate with VD levels. These findings provide additional evidence for the development of low-cost preventive and therapeutic strategies. [Image: see text] DISCLOSURES: All authors: No reported disclosures.