Immunity and vaccines

• Active immunity: the type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen
• There are two types of active immunity:

  1. natural - this is when yo become immune after catching a disease
  2. artificial - this is when you become immune after you've been given vaccination containing a harmless dose of antigen
• Passive immunity: the type of immunity you get from being given antibodies made by different organism - your immune system doesn't produce any antibodies of its own
• 2 types of passive immunity:

  1. natural - this is when a baby becomes immune due to the antibodies it receives from its mother, through the placenta and in breast milk
  2. artificial - this is when you become immune after being injected with antibodies from someone else e.g. if you contract tetanus you can be injected with antibodies against the tetanus toxin, collected from blood donations
• Active immunity

  1. requires exposure to antigen
  2. it takes a while for protection to develop
  3. memory cells are produced
  4. protection is long-term because the antibody is produced (after activation of memory cells) in response to complementary antigen being presented in the body
• Passive immunity:

  1. doesn't require exposure to antigen
  2. protection is immediate
  3. memory cells are not produced
  4. protection is short-term because the antibodies given are broken down
• Vaccination: While your B-cells are dividing to build up their numbers to deal with a pathogen (i.e. the primary response), you suffer from a disease - vaccination can help avoid this
• Vaccinations contain antigens that cause the body to produce memory cells against a particular pathogen, without the pathogen causing disease - means that you become immune without getting any symptoms
• Vaccines protect individuals that have them and, because they reduce the occurrence of the disease, those not vaccinated are also less likely to catch the disease (because there are fewer people to catch it from) - herd immunity
• Vaccines always contain antigens - these may be free or attached to a dead or attenuated (weakened) pathogen. Vaccines may be injected or taken orally
• The disadvantaged of taking a vaccine orally are that it could be broken down y enzymes in the gut or the molecules of the vaccine may be too large to be absorbed into the blood.
• Sometimes booster vaccines are given later on (e.g. after several years) to make sure that memory cells are produced
• Ethical issues: all vaccines are tested on animals before being tested on humans - some people disagree with animal testing. Also animal based substances may be used to produce a vaccine, which some people disagree with
• Testing vaccines on humans can be risky e.g. volunteers may put themselves at unnecessary risk of contracting the disease because they think they're fully protected (e.g. they might have unprotected sex because they have had a new HIV vaccine and think they're protected - and the vaccine might not work)
• Some people don't want to take the vaccine due to the risk of side effects, but they are still protected because of herd immunity - other people think this is unfair
• In there was an epidemic of a new disease (e.g. a new influenza virus) there would be a rush to receive a vaccine and difficult decisions would have to be made about who would be the first to receive it