| Smallpox vaccine contains live vaccinia virus, a milder cousin of the variola virus. |
| Jenner waited only four years before declaring that the vaccine that he named vaccinia provided immunity from smallpox for life. |
| The view that vaccinia is attenuated variola is well known, and has been extensively adopted by English physicians. |
| Other viruses in this group that can cause infection in humans include variola, vaccinia, and cowpox viruses. |
| A live, replicating virus, vaccinia can cause side effects, which on rare occasions can be serious and potentially life-threatening. |
| The live vaccinia virus that is used for the smallpox vaccination is admittedly the most dangerous vaccine in use. |
