CIE IGCSE Biology

Revision Notes

10.3 Vaccination

What is Vaccination?

  • Vaccinations give protection against specific diseases and boost the body’s defence against infection from pathogens without the need to be exposed to dangerous diseases that can lead to death
  • The level of protection in a population depends on the proportion of people vaccinated
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How does Vaccination Work?

  • Vaccines allow a dead or altered form of the disease-causing pathogen, which contains specific antigens, to be introduced into the body
  • In this weakened state, the pathogen cannot cause illness but can provoke an immune response
  • Lymphocytes produce complementary antibodies for the antigens
  • The antibodies target the antigen and attach themselves to it in order to create memory cells
  • The memory cells remain in the blood and will quickly respond to the antigen if it is encountered again in an infection by a ‘live’ pathogen
  • As memory cells have been produced, this immunity is long-lasting

 

Vaccination, IGCSE & GCSE Biology revision notesVaccination

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How does Vaccination Control the Spread of Disease

  • If a large enough percentage of the population is vaccinated, it provides protection for the entire population because there are very few places for the pathogen to breed – it can only do so if it enters the body of an unvaccinated person
  • This is known as herd immunity
  • If the number of people vaccinated against a specific disease drops in a population, it leaves the rest of the population at risk of mass infection, as they are more likely to come across people who are infected and contagious
    This increases the number of infections, as well as the number of people who could die from a specific infectious disease

 

Herd_immunity, IGCSE & GCSE Biology revision notesHerd immunity

 

  • Herd immunity prevents epidemics and pandemics from occurring in populations
  • This is the reason that many vaccinations are given to children, as they are regularly seen by medical practitioners and can be vaccinated early to ensure the entire vaccinated population remains at a high level
  • In certain instances, vaccination programmes are run with the aim of eradicating certain dangerous diseases, as opposed to controlling them at low levels
  • An example of a disease which has been eradicated as a result of a successful vaccination programme is smallpox, which was officially eradicated in 1980 after a vaccination programme run by the World Health Organisation since the mid-1950s

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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