Once the system is in place to "do something about it", the attackers will just move on to something else. Airplanes were used, then airline security was tightened...but too late. Anthrax is being used, now drug companies are distributing medication...but too late. Once the anti-Antrhax system is in place, the terrorists will be attacking one of a host of other under-protected fear-generating spots.
Antrax is a poor choice for a weapon of mass distruction. It has been used well in this situation as a weapon of mass hysteria.
If terrorists choose to kill a great number of people (and I'm not conviced that that is their goal), they will use an infectious disease -- like Small Pox. Small Pox is a CDC nightmare.
Small Pox vaccinations stopped many years ago. Most young people would be entirely unprotected. The medical community is unsure whether the vaccinated masses would be resistant to newer strains or even to the original strain. Not having the disease around for people to fight off has brought the efficacy of the vaccination into question.
Distribution of Small Pox would be easily accomplished, and would produce an pandemic.
Yes true, but now the level of hysteria is sufficient that a crop duster dropping nothing more than flour over a stadium will have us killing one another in an effort to reach the street. (And flour can be obtained almost anywhere.)