Vaccine Types

Vaccines are biological preparations, often made from attenuated or killed forms of microorganisms or fractions thereof. They work by stimulating the immune system to produce antibodies and cells directed against a particular organism, mimicking "natural infection". Based on their biological and chemical characteristics, vaccines can be categorized into two basic types, "Live-attenuated" (bacterial or viral) vaccines and "inactivated" or "non-live" vaccines. Examples of live-attenuated vaccines include: measles-, mumps-, and rubella-, varicella-, yellow fever-, oral polio- (OPV), rotavirus-, ("nasal-spray") live-attenuated influenza- (LAIV), and BCG-vaccine. Attenuation results in micro-organisms that may still infect and multiply in humans, but they do not cause disease. Some of these vaccines are associated with life-long immunity. Inactivated or non-live vaccines include those against hepatitis A, influenza, pertussis, rabies or the polysaccharide vaccines directed against encapsulated bacteria (Haemophilus influenzae type b, Streptococcus pneumoniae, Neisseria meningitidis). Most non-live vaccines generally require additional doses ("boosters") to maintain long-term protective immunity. There are many other subcategories of these basic groups, like subunit vaccines, whole cell vaccines, toxoid vaccines, polysaccharide vaccines, recombinant protein vaccines, mucosal vaccines, or DNA-, mRNA- and vector-vaccines.