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Vitamin D study #1 of 50
2010 Pre-Exposure Prophylaxis study (treated before exposed to the virus)
Urashima et al., Am. J. Clin. Nutr. 2010, 91:5, 1255-60, doi:10.3945/ajcn.2009.29094 (Peer Reviewed)
Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren
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RCT for vitamin D supplementation and seasonal influenza A in schoolchildren, showing 10.8% incidence in children in the vitamin D3 group compared with 18.6% in the placebo group, relative risk RR 0.58 [0.34-0.99], p = 0.04.
The reduction was more prominent in children who had not been taking other vitamin D supplements. RR 0.36 [0.17-0.79], p 0.006, and who started nursery school after age 3y, RR 0.36 [0.17-0.78], p = 0.005.
Reduced incidence of influenza B was not seen, RR 1.39 [0.90-2.15], p = 0.13.

Urashima et al., 1/1/2010, peer-reviewed, 6 authors.
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