People around 30 and under in this country were never vaccinated against small pox because it has been eradicated as a communicable disease caught in normal circumstances.
Those older who were vaccinated, everyone pretty much, may have become non-immune over time. So most people would be susceptible to small pox if an outbreak occurred. It is a particularly nasty disease and killed about 30% of the people it infects.
As far as the threat, the Russians grew vats of it as a bio warfare agent. This means it is still around somewhere somehow. Terrorists could get their hands on it, potentially.
But even if they couldn't get it from Russians, it is conceivably available for Iraq. The only known internationally agreed upon stock of the virus is in Atlanta at the CDC and in Russia. These were kept as a repository of a dead disease. There had been plans to destroy this last remaining stock. This is not where Iraq could get it.
But, there are ways Iraq could get and develop it completely inside their own country that are not far out or difficult to imagine.
I think that the small pox vaccines are pre-cautionary, but perhaps there is intelligence that is classified that indicates it is more than a potential threat.
Anyways, it is a good idea to do this and I believe we should begin standard vaccinations again like we did for centuries as a precaution.