given that vit D(3) is immunosuppressive, er, immunomodulatory... and that the study involved antigen testing for viral infection... whether the Vit d(3) simply blocked the immune response to the virus so that insufficent antigens were produced to show positive on test... yes my tin foil hat is on here... but in my own health battles, I had to uncover viruses that lay hidden from immune system... no immune response. this appears to be the ultimate purpose of the walmart style push to have the entire world declared vit d deficient... turn off the immune system, let the germs quietly take over...