I think people should be screened, because there are people who would react adversely even to this virus, I am all for doing that and making informed decisions.
But also remember, that the vaccine used to be mandatory -- yes, this very same vaccine -- and there were no major casualties from it.
I think the vaccine should be made available, so those who want it, can discuss it with their doctors and get it, if they so choose. And those who choose to not take it, would be able to opt for that too.
The main issue is, that if we do have a terrorist attack, it won't be like a natural spread, where one person gets it, but there will be hundreds, even thousand coming down with it all at once, so trying to vaccinate everyone everywhere will be totally impossible, just think, regardless of what they are claiming.
But if a large fraction, as in most people have already been vaccinated, that would stop and slow down the spread, and protect to some extent, even those who aren't vaccinated.
Also, if someone is likely to have a problem as a result of a vaccine, the best time to have it is when there is no panic, and they could have extra medical attention ( they also have specific immune globulin against vaccinia, which would help the immune systems of those having a negative reaction). If someone has a negative reaction to the vaccine, when thousands of people are coming down with real smallpox, I don't think they will get all the care they need, just because it won't be physically possible.
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How dangerous is smallpox?
Historically, smallpox killed about 30 percent of those infected. The mortality rate varied with age (with small children and the elderly proving the most vulnerable) and with the strength of a person’s immune system (with preexisting illness or malnutrition making one more susceptible). Less frequently, complications such as encephalitis (an inflammation of the brain) and blindness also resulted. Smallpox is one of the most devastating diseases known to humankind, having killed between 300 and 500 million people in the twentieth century alone.
From:
http://www.terrorismanswers.com/weapons/smallpox.html