Vaccination (AQA GCSE Biology): Revision Note

Why vaccinate?

• Vaccination can prevent illness in individuals, as well as preventing the spread of pathogens within a population

• If a large number of the population are vaccinated, fewer people in the population have the disease, so the pathogen is less likely to be passed on, and even unvaccinated people are less likely to come into contact with someone who has it

  • This is the principle of herd immunity

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Evaluating vaccination

Advantages:

• Smallpox has been eradicated in the global population due to a successful vaccination programme

• Diseases that were once common are now relatively rare due to widespread vaccinations, e.g.:

  • polio

  • measles

• Epidemics can be prevented if a large number of the population are vaccinated

Disadvantages:

• The vaccine may not be 100 % effective

• Vaccines may result in side-effects, such as:

  • pain at the injection site

  • flu-like symptoms

• Vaccines are only effective if enough of the population is vaccinated

  • People choosing not to be vaccinated can therefore cause resurgence of a disease

How do vaccines work?

• Vaccination involves:

  1. introducing small quantities of dead or inactive forms of a pathogen into the body

  2. the stimulation of white blood cells to produce specific antibodies

     • this is the primary response

  3. the white blood cells responding quickly to produce the correct (specific) antibodies if the same pathogen enters the body again; these antibodies destroy the pathogen before it can cause illness

     • this is the secondary response

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Measuring antibody production

• We would expect to see:

  • A small peak of antibody production a few days after vaccination, which then falls; this is the primary response

  • A second, larger, steeper peak of antibody production after coming into contact with the same pathogen again; this is the secondary response

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