Vaccines

• Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. Vaccines reduce the occurrence of the disease, those not vaccinated are also less likely to catch the disease- this is called herd immunity.
• Vaccinations are sometimes called immunisations.
• Vaccines always contain antigens- these may be free or attached to a dead or attenuated pathogen. Vaccines may be injected or taken orally. The disadvantages of taking vaccines orally are that it could be broken down by enzymes in the gut or the molecules may be too large to be absorbed into the blood. Sometimes booster vaccines are given to make sure that more memory cells are produced. Attenuated viruses have usually been genetically or chemically modified so that they can't produce toxins or attach to the infected host cells.
• Ethical Issues:

  • Animal Testing
  • Personal Beliefs
  • Uncertainty
• Antigenic Variation: Pathogens can change their surface antigens. This means that when you're infected for a second time the memory cells produced from the first infection will not recognise the different antigens. So the immune system has to carry out a primary immune response.

  Antigenic variation also makes it difficult to develop vaccines against some pathogens for that reason. Pathogens of the same type that show antigenic variation are often referred to as strains.