The term "immunizer" refers to a substance or agent that helps to boost the body's natural immunity against infections or diseases. Synonyms for this term include "vaccine," "serum," "antitoxin," "immunogen," "antibody," and "immunomodulator." Vaccines contain weakened or dead pathogens that stimulate the production of antibodies in the body, while serums and antitoxins contain preformed antibodies to neutralize specific toxins produced by bacteria. Immunogens are substances that can stimulate an immune response and create an immune memory, while antibodies play a vital role in the immune system by recognizing and targeting specific pathogens. Immunomodulators help to regulate and boost the immune system's overall response to infections and diseases.