Vaccinations

• 𝙑𝘼𝘾𝘾𝙄𝙉𝘼𝙏𝙄𝙊𝙉𝙎:

  FOR

  • prevents a second infection
  • can reduce the risk of disease caused by infection

  AGAINST

  • costly
  • antigenic variability issue
  • research in mice cannot always be replicated in humans
• Why are vaccinations important?

  Some bacteria and viruses can cause significant harm while the primary response is happening (before the secondary response kicks in and antibody concentration increases).

  E.g. cholera and smallpox.
• A vaccine contains antigens derived from pathogenic organisms. Some vaccines contain just the antigen, while some contain weakened forms of the virus or bacteria that cause the disease.
• When injected into an individual, the antigen in the vaccine stimulates a primary response that leaves memory cells to generate the secondary response if the individual is subsequently infected by the relevant pathogen.
• Infection and vaccination give active immunity against a disease - the person is exposed to the antigen, and makes their own antibodies against it, retaining memory cells for long-lasting immunity.
• Many childhood vaccinations are given in two doses, separated by several months or years. Suggest why this is done.

  The first vaccination elicits a primary response and the second 'booster' dose elicits a secondary response. This produces more antibodies and memory cells, providing better protection against the disease than could be achieved with a single injection.
• The first time an antigen is encountered, a primary response is elicited. On the second encounter with the antigen, a secondary response is elicited.
• The secondary response is faster than the primary response and produces greater quantities of antibodies. This is because memory cells specific to that antigen are already present in the body.
• Although we develop immunity to each strain of the cold or influenza virus that we are exposed to, new strains are constantly being produced, and their antigens are not the same (high antigenic variability).
• Vaccination introduces harmless antigens into the body, causing a primary response and the production of memory cells, without causing illness.
• Active immunity is the result of the immune system's response to antigens and involves the production of antibodies and memory cells.
• Passive immunity is the result of acquiring antibodies from another organism (e.g. a baby's mother) and does not involve the production of antibodies or memory cells.
• Herd immunity results if enough members of a population have immunity to a particular pathogen (e.g. they've been vaccinated against it) to make it difficult for the pathogen to pass from one non-immune person to another.