Not sure. I am not sure whether antioxidants would be good or bad when taken with sodium selenite. The study I quoted above (this one) says that the antiviral effects of sodium selenite comes from its interaction with thiols (which are sulfur compounds). The chemical reaction between sodium selenite and thiols is:ᐞ Sodium selenite + thiol => hydrogen selenide + several selenium-containing compounds + reactive oxygen species. It is the hydrogen selenide produced in this reaction that is responsible for the sodium selenite toxicity. So I presume it is ether the hydrogen selenide, the selenium-containing compounds, or the reactive oxygen species produced in this reaction that has the antiviral effects. In the case of sodium selenite's anti-cancer effects, I believe it is the hydrogen selenide produced by taking sodium selenite that kills the cancer cells.