(12-05-10) Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren1,2,3

Mitsuyoshi Urashima, Takaaki Segawa, Minoru Okazaki, Mana Kurihara, Yasuyuki Wada and Hiroyuki Ida

1 From the Division of Molecular Epidemiology (MU)the Department of Pediatrics (MU YWHI) Jikei University School of Medicine Minato-ku Tokyo Japan; the Department of Pediatrics Fuji City General Hospital Shizuoka Japan (TS); the Department of Pediatrics Sado General Hospital Sado City Niigata Japan (MO);the Department of Pediatrics Kanagawa Rehabilitation Center Kanagawa Japan (MK).
2 Supported by the Jikei University School of Medicine.
3 Address correspondence to M Urashima, Division of Molecular Epidemiology, Jikei University School of Medicine, Nishi-shimbashi 3-25-8, Minato-ku, Tokyo 105-8461, Japan. E-mail: [email protected] .
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 D3 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 D3 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 D3 compared with 12 children receiving placebo (RR: 0.17; 95% CI: 0.04, 0.73; P = 0.006).
Conclusion: This study suggests that vitamin D3 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.

Source: Am J Clin Nutr 91: 1255-1260, 2010.

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