Edexcel GCSE Combined Science: Biology

Revision Notes

5.2.3 Vaccination


  • Vaccines are used to induce immunity to infectious diseases
  • A vaccine contains harmless versions of a pathogen
  • There are several different methods by which scientists ensure that vaccines contain harmless pathogens such as:
    • Killing the pathogen
    • Making the pathogen unable to grow or divide (attenuated vaccine)
    • Using fragments of pathogens, which include the necessary antigens (rather than whole cells)
  • A vaccine may be administered orally, nasally or via an injection

How vaccines work

  • Once in the bloodstream, the antigens contained within the vaccine can trigger an immune response in the following way:
    • Lymphocytes recognise the antigens in the bloodstream
    • The activated lymphocytes produce antibodies specific to the antigen encountered
    • Memory cells and antibodies subsequently remain circulating in the blood stream

Vaccination, IGCSE & GCSE Biology revision notes

The process of long-term immunity by vaccination

  • Future infection by the same pathogen will trigger a response that is much faster and much larger compared to the initial response
  • Due to the rapid nature of the response, the pathogen is unable to cause disease and the individual is said to be immune

Vaccination graph, downloadable IGCSE & GCSE Biology revision notes

Graph showing the number of measles antibodies in the blood following vaccination. The secondary response is much faster and a greater number of antibodies are produced.

Author: Ruth

Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. With 10 years of teaching experience across the 3 key science disciplines, Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.

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