|A vaccine is any preparation intended to produce immunity to a disease by stimulating the production of antibodies. Vaccines include, for example, suspensions of killed or attenuated microorganisms, or products or derivatives of microbs. The common method of administering vaccines is by injection, but some are given by mouth or nasal spray. Essentially vaccines help reduce the risk of a disease by introducing a killed or attenuated version of the disease-causing organism to the bodyâs immune system. If immune system encounters the disease-causing germ, quick recognition allows our body to fight infection with a rapid and effective immune response. In this way, vaccines mimic the bodyâs natural immunity.Types of vaccines.Live attenuated vaccines: Consist of weakened viruses or bacteria that the immune system cannot differentiate from a stronger, naturally occurring infection and consequently mounts a strong response similar to that induced by the natural disease. E.g. Influenza (nasal spray) Rotavirus.Inactivated vaccines: Contain either whole or portions of killed bacteria or viruses and require several doses, generally to prime the immune system and then boost the immune response to provide protection. E.g. Rabies Toxoid vaccines: Contain toxins produced by bacteria that have been inactivated to avoid toxic effects while producing a protective immune response. E.g. Diphtheria, tetanusSub-unit vaccines: Consist of specific proteins purified from viruses or bacteria that are capable of generating an immune response. E.g. Pneumococcal, Meningococcal. Polysaccharide vaccines: Contain purified sugar molecules taken from the surface of bacteria that can stimulate the immune system to generate antibodies. E.g. Meningococcal. Conjugate vaccines: Contain polysaccharides joined to immunestimulating molecules to develop a more robust immune response. E.g. Haemophilusinfluenzaeb,meningococcal, pneumococcal,typhoid. Recombinant vaccines: Recombinant vaccines are created by utilizing bacteria or yeast to produce large quantities of a single viral or bacterial protein. This protein is then purified and injected into the patient, and the patient's immune system makes antibodies to the disease agent's protein, protecting the patient from natural disease.