Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren.
What this study found
Vitamin D3 supplementation reduced seasonal influenza A incidence versus placebo. Influenza A occurred in 18/167 children (10.8%) in the vitamin D3 group and 31/167 (18.6%) in the placebo group, corresponding to RR 0.58 (95% CI, 0.34 to 0.99; P = 0.04). Benefits were larger in children not taking other vitamin D supplements (RR 0.36; 95% CI, 0.17 to 0.79; P = 0.006) and in those who started nursery school at age 3 years or older (RR 0.36; 95% CI, 0.17 to 0.78; P = 0.005). Asthma attacks were also reduced among children with asthma (2 vs 12; RR 0.17; 95% CI, 0.04 to 0.73; P = 0.006), while…
- Study & population
- Randomized, placebo-controlled trial in Japanese schoolchildren aged 6 to 15 years recruited from 12 hospitals and 8 private practices.
- Intervention
- Oral vitamin D3 (Status D3), 1200 IU/day total, given as 3 tablets twice daily from 1 December 2008 to 31 March 2009.
- Key limitation
- Follow-up was limited to one winter season, so durability and reproducibility are uncertain.
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Open PDFOriginal abstract
BACKGROUND To our knowledge, no rigorously designed clinical trials have evaluated the relation between vitamin D and physician-diagnosed seasonal influenza. OBJECTIVE We investigated the effect of vitamin D supplements on the incidence of seasonal influenza A in schoolchildren. DESIGN From December 2008 through March 2009, we conducted a randomized, double-blind, placebo-controlled trial comparing vitamin D(3) supplements (1200 IU/d) with placebo in schoolchildren. The primary outcome was the incidence of influenza A, diagnosed with influenza antigen testing with a nasopharyngeal swab specimen. RESULTS Influenza A occurred in 18 of 167 (10.8%) children in the vitamin D(3) group compared with 31 of 167 (18.6%) children in the placebo group [relative risk (RR), 0.58; 95% CI: 0.34, 0.99; P = 0.04]. The reduction in influenza A was more prominent in children who had not been taking other vitamin D supplements (RR: 0.36; 95% CI: 0.17, 0.79; P = 0.006) and who started nursery school after age 3 y (RR: 0.36; 95% CI: 0.17, 0.78; P = 0.005). In children with a previous diagnosis of asthma, asthma attacks as a secondary outcome occurred in 2 children receiving vitamin D(3) compared with 12 children receiving placebo (RR: 0.17; 95% CI: 0.04, 0.73; P = 0.006). CONCLUSION This study suggests that vitamin D(3) supplementation during the winter may reduce the incidence of influenza A, especially in specific subgroups of schoolchildren. This trial was registered at https://center.umin.ac.jp as UMIN000001373.