The report has evoked much public concern. In some of the reports, there were misconceptions about the components of the vaccine used to prevent smallpox, and about why any country might still be retaining stocks of smallpox vaccine. This note aims to clarify these issues. Smallpox vaccine is not made from smallpox virus. The vaccine which was used for centuries to vaccinate against smallpox was not made from smallpox, but from vaccinia virus.
Vaccinia is a different virus from the virus which causes smallpox.
However, it is a member of the same family of viruses to which the smallpox virus belongs. The smallpox virus is also known as variola virus. Mass vaccinations with smallpox vaccine made from vaccinia virus led to the eradication of smallpox announced by WHO in 1980. These are the WHO Collaborating Centres in Atlanta, USA and Koltsovo, Russian Federation. This recommendation has been made for two reasons.