There are two forms of smallpox: variola major, which is the more severe form, and variola minor, which is less common and generally less severe. Variola major had a mortality rate of about 30% ...

[9] Variola major, which is more severe and most common ... Nonemergency Administration of Smallpox Vaccine June 2001, and Summary of October 2002 ACIP Smallpox Vaccination Pre-event ...