http://www.ajcn.org/cgi/content/abstract/91/5/1255?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=Mitsuyoshi+Urashima&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
A Japanase study shows an 8% reduction in incidence of Influenza A in school children who were given 1200 IU Vitamin D per day preventatively during the fall periode. This was compared to a control group given a placebo treatment (designed to have absolutely no effect). Considering the importance of Vitamin D in a host of other processes, making sure kids get adequate Vitamin D seems like a smart move. Not sure how many studies there are on the efficacy of flu-vaccines, will have to look for that.