U.S. Department of Defense scientists have developed a vaccine for ricin, an easily manufactured biological weapon. Ricin, a concentrated poison derived from castor beans, has long been listed as one of the more easily manufactured biological weapons. Basically, ricin is a concentrated poison, some 6,000 times more lethal than cyanide. A dose the size of a grain of salt can kill an adult human. The victim can either inhale or digest a lethal dose of ricin. Ricin can also be absorbed through the skin if it is mixed with a suitable solvent (like DMSO). In the past, ricin has only been used for assassinations by the secret police of the Soviet Union. But several al Qaeda groups have been caught processing castor beans to produce small amounts of ricin. Despite its concentrated toxicity, you still need a lot of ricin to have it perform as a weapon of mass destruction. For example, it would take a ton of ricin, in aerosol form, to kill half the people in an area five kilometers by five kilometers. However, if you got ricin into the food or water supply, the effects would not be as lethal, but massive illness would certainly terrorize. Al Qaeda may have been producing small amounts of ricin for use in assassinations. The vaccine would be useful for those who have to investigate ricin manufacturing operations and might accidentally be exposed to the poison.