Ooookay. Yet another substance that I will not allow to be injected into my children by government fiat.
I can take a large amount of preventive measure to protect my family from infection, and I'm not worried about a lethal virus transforming into the airborne vector.
Were such a thing to happen in a manner that was not limited by its own lethality (Ebola), the human race would have been long extinct, human intervention by antiviral or not.
However, viruses do not progress/mutate in that exact manner.