Changes

*Killed inactivated organism or toxin (toxoid)

*Killed inactivated organism or toxin (toxoid)

**Virulent and toxic organisms cannot be used as vaccines as they would cause disease

**Virulent and toxic organisms cannot be used as vaccines as they would cause disease

**Organisms can be killed using radiation or chemicals so that they still posess the antigens to stimulate an immune response, but the organisms are unable to replicate inside the host

**Organisms can be killed using radiation or chemicals so that they still possess the antigens to stimulate an immune response, but the organisms are unable to replicate inside the host

**Toxins are inactivated to produce a toxoid which will still have the antigens needed to produce an immune reponse but will not be harmful to the host

**Toxins are inactivated to produce a toxoid which will still have the antigens needed to produce an immune reponse but will not be harmful to the host

**Needs two doses

**Needs two doses