More disturbing are the potential complications from the vaccine. This can include blindness caused by touching the vaccination site when the virus is shedding, then rubbing the eye.
Mortality rates from smallpox (roughly 30%) were estimated in the period prior to widespread antibiotic availability for the common secondary infections.
The India 1 strain of Smallpox which the Soviets weaponised causes the haemorraghic form of the disease. Its mortality rate is more like 70%. If al-Qaeda have a stock of Smallpox they are most likely to have this strain.