Preventive Effects of Vitamin D on Seasonal Influenza A in Infants: A Multicenter, Randomized, Open, Controlled Clinical Trial

Objectives: This study aimed to evaluate the clinical efficacy and safety of vitamin D for preventing influenza A in 400 infants in a multicenter, randomized, open, controlled clinical trial. Methods: The infants were randomized into low-dose and high-dose vitamin D groups, and serum calcium, inorganic phosphorus and 25-hydroxyvitamin D levels were detected thrice in 4 months. Infants infected with influenza A were monitored for symptoms including fever, cough and wheezing. Pathogen levels and safety of vitamin D treatment were also evaluated. Results: Of 121 cases in total, 78 and 43 cases of influenza A infection occurred in the low-dose and high-dose vitamin D groups, respectively. There was a significant difference between the groups ((2) = 14.6324, P = 0.0001). Among the cases of influenza infection, the median durations for fever, cough and wheezing were shorter in the high-dose vitamin D group than in the low-dose vitamin D group. The viral loads showed a downward trend in both groups and were significantly different between the groups at the second and third detections. Additionally, the incidences of adverse events and severe adverse events were very low and not significantly different between the 2 groups. Conclusion: High-dose vitamin D (1200 IU) is suitable for the prevention of seasonal influenza as evidenced by rapid relief from symptoms, rapid decrease in viral loads and disease recovery. In addition, high-dose vitamin D is probably safe for infants.