“…It was reported that no pyrogenicity was found with vaccinia virus (King, 1962 ) and also with poliovirus and echo virus (Siegert, 1967 ; Grossgebauer, 1967 ). Subsequently, regarding the pathogenicity of fever in rabbits infected intradermally with vaccinia virus, some evidence was presented suggesting that early humoral antibodies were involved in the induction of fever (Grossgebauer, 1972 ). More recently, it was demonstrated that several vaccinia virus strains, including smallpox vaccines that express soluble IL-1 receptors, which bind IL-1β but not IL-1α, prevent the febrile response in infected mice, whereas strains that lack the receptor naturally or through genetic engineering induce fever, and that the vaccinia virus-induced fever is inhibited with antibodies to IL-1β (Alcami & Smith, 1996 ).…”