Abstract
Inactivated vaccinia virus vaccines were prepared from purified virus inactivated by either formalin, hydroxylamine or heat. The immunogenicity of these vaccines was assessed in rabbits by measurement of virus neutralizing antibody following each of two inoculations. It was concluded that inactivated vaccinia virus stimulates the production of neutralizing antibody and that the most important single factor in this immunogenicity is the concentration of virus in the vaccine. Vaccines prepared from virus suspensions containing 107 to 108 pfu/ml. before inactivation give variable antibody responses.