The two major vaccines use killed viruses that are not infectious.

These vaccines use only the capsid proteins of the virus.

Later, and still today, another vaccine was used: vaccinia.

"Haffkine's vaccine used a small amount of the bacteria to produce an immune reaction."

In fact, he said, such vaccines could use some tinkering as well.

The first vaccine for smallpox used the results of cowpox infections.

The vaccine that helped eradicate smallpox used a weakened virus.

The vaccine uses a synthetic version of a ganglioside protein commonly found on melanoma cells.

This vaccine used a live virus grown in rabbits, and weakened (through drying it).

The vaccine uses a live virus similar to smallpox that can by itself cause infections and, in rare cases, death.