A vaccine is a biological preparation that provides active acquired immunity to a particular disease.
- A vaccine typically contains an agent that resembles a disease causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins.
- Types of vaccines are;
- Active vs. Passive Immunization vaccines
- Designing Vaccines
- Whole-Organism Vaccines
- Purified Macromolecules as Vaccines
- Recombinant-Vector Vaccines
- DNA Vaccines
- Synthetic-Peptide Vaccines
- Mulvivalent Subunit Vaccines
- Killed
- Some vaccines contain killed, but previously virulent, micro-organisms that have been destroyed with chemicals, heat, radioactivity or antibiotics.
- Examples are the influenza vaccine, cholera vaccine, bubonic plague vaccine, polio vaccine, hepatitis A vaccine, and rabies vaccine.
- Attenuated
- Some vaccines contain live, attenuated microorganisms.
- Although most attenuated vaccines are viral, some are bacterial in nature.
- Examples include the viral diseases yellow fever, measles, rubella, and mumps and the bacterial disease typhoid. The live Mycobacterium tuberculosis vaccine developed by Calmette and Guérin is not made of a contagious strain, but contains a virulently modified strain called “BCG” used to elicit an immune response to the vaccine. The live attenuated vaccine containing strain
- Toxoid
- Toxoid vaccines are made from inactivated toxic compounds that cause illness rather than the micro-organism.
- Examples of toxoid-based vaccines include tetanus and diphtheria.
- Toxoid vaccines are known for their efficacy.
- Not all toxoids are for micro-organisms; for example, Crotalus atrox toxoid is used to vaccinate dogs against rattlesnake bites.
- Subunit
- Protein subunit rather than introducing an inactivated or attenuated micro-organism to an immune system (which would constitute a “whole-agent” vaccine), a fragment of it can create an immune response.
- Conjugate
- Conjugate – certain bacteria have polysaccharide outer coats that are poorly immunogenic.
- By linking these outer coats to proteins (e.g. toxins), the immune system can be led to recognize the polysaccharide as if it were a protein antigen.
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