Immunization

Abstract

PREVENTION of disease by immunization predates knowledge of infection or immunology in human history. Inoculation of smallpox material intranasally in an effort to prevent smallpox was first noted in 590 BC in the Sung dynasty. From such empiric beginnings are derived immunization practices, built on centuries of casual and painstaking observation, intuition, and scientific experiment. Current immunization practices are based on immunologic aspects of the host response, state of microbiological technology, restraints of practicality, and economic, ethical, and medicolegal considerations. The recent elimination of smallpox represents the final chapter in a 2500-year history of vaccination that has included all of the aforementioned factors.¹The routine prevention of infectious diseases in children or select high-risk adult populations represents one of the outstanding accomplishments of medical science. <h3>ACTIVE IMMUNIZATION</h3> Active immunization is based on the premise that immunologic mechanisms appropriate for defense against microorganisms can be evoked in the absence of