Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren.
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.


METHODS
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).


CONCLUSIONS
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.
Urashima
Mitsuyoshi
M
Division of Molecular Epidemiology, Jikei University School of Medicine, Nishi-shimbashi 3-25-8, Minato-ku, Tokyo 105-8461, Japan. urashima@jikei.ac.jp
Segawa
Takaaki
T
Okazaki
Minoru
M
Kurihara
Mana
M
Wada
Yasuyuki
Y
Ida
Hiroyuki
H
D000293:Adolescent; D001827:Body Height; D001835:Body Weight; D002648:Child; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D009980:Influenza A virus; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D007564:Japan / Q000453:epidemiology; D008297:Male; D018579:Patient Selection; D010919:Placebos; D012306:Risk
D010919:Placebos; D002762:Cholecalciferol