Although the main weapon used was vaccinia virus, which was used as the vaccine, no one seems to know exactly where vaccinia virus came from; it is not the strain of cowpox that Edward Jenner used, and it is not a weakened form of smallpox.
Kuigi peamiseks relvaks oli vaktsiinina kasutatud vaktsiinia viirus, ei ole täpselt teada, kust see viirus tuli; seda ei kasutanud Edward Jenner ja see ei ole ka rõugete nõrgestatud vorm.