more science:
"Hypovitaminosis D is a deficiency of Vitamin D." http://en.wikipedia.org/wiki/Hypovitaminosis_D
"Vitamin D" http://en.wikipedia.org/wiki/Vitamin_D
"Recently, Cannell and colleagues have suggested that vitamin D deficiency is a major risk factor for influenza and that vitamin D may be effective in reducing influenza incidence and severity." http://en.wikipedia.org/wiki/Vitamin_D_and_influenza