Active and passive immunity, vaccine types, excipients and licensing.

Abstract Immunity is the state of protection against infectious disease conferred either through an immune response generated by immunization or previous infection or by other non-immunological factors. This article reviews active and passive immunity and the differences between them: it also describes the four different commercially available vaccine types (live attenuated, killed/inactivated, subunit and toxoid): it also looks at how these different vaccines generate an adaptive immune response.