The introduction of vaccination has been one of the most decisive advances leading to the dramatic downward trend in the incidence of many viral diseases. The principle of vaccination is to induce a “primed” state in the vaccinated subject so that, following exposure to a pathogen, a rapid secondary immune response is generated leading to the accelerated elimination of the organism and protection from clinical disease. Success depends on the generation of memory T and B cells and the presence in the serum of neutralizing antibody. Attributes of a good vaccine • Ability to elicit the appropriate immune response for the particular pathogen: Tuberculosis—cell mediated response , Most bacterial and viral infections—antibody • Long term protection ideally life-long • Safety vaccine itself should not cause disease • Stable retain immunogenicity, despite adverse storage conditions prior to administration • Inexpensive . Types of Vaccine: Vaccines in general use includes: LIVE vaccines; and KILLED vaccines.
