vaccination (vacc) /vak′sinā″shən/ [L, vaccinus, relating to a cow] , any injection of attenuated or killed microorganisms, such as bacteria, viruses, or rickettsia, administered to induce immunity or to reduce the effects of associated infectious diseases. Historically the first vaccinations were administered to immunize against smallpox. Vaccinations are now available to immunize against many diseases, such as diphtheria, measles, and mumps. −vaccinate, v.
