An update on smallpox vaccine candidates and their role in bioterrorism related vaccination strategies.

The threat of using variola virus in a bioterrorist attack urged different countries to renew the production of traditional vaccines and develop new generations of smallpox vaccines. Manufacturers try to combine smallpox vaccine past experience with technological advances in vaccine development to achieve protection similar to that of the traditional vaccines with a higher level of safety and fewer contraindications. In light of the reported immunogenicity and reactogenicity of the stockpiled smallpox vaccines employed in the last immunization campaigns of "first responders", we review recently accumulated data on the assessment of new smallpox vaccine candidates and discuss their role in possible vaccination policies.