No, but the feasibility of engineering viruses (which is simple in the movies) is unclear. I myself doubt that viruses can be made more virulent without damaging them in other ways.
>>Also, we do not have to be innoculated UNLESS there is absolute certainty that we are being exposed....correct?????<<
The State cannot require you to be immunized, but they can quarantine you against your will if you refuse.
I don't think vaccine refusal is going to be much of an issue after an attack...