QUOTE : Through my research on this topic, I have found that the vaccinated immature (children, puppies, kittens) end up with increased gamma interferon levels. Gamma interferon levels will do two significant things: one, it will increase the gastrointestinal <br />tract permeability allowing more bacteria and viruses to pass across into the bloodstream and two, there will be a decrease in the number of the cell mediated T-cells that are in charge of attacking parasites.