11.2.4

Vaccines

Test yourself

Vaccination

Vaccines help the immune system recognise and destroy pathogens.

Illustrative background for Insertion of antigensIllustrative background for Insertion of antigens ?? "content

Insertion of antigens

  • Vaccines insert the antigens for a specific disease into the individual.
  • The antigens can be inserted by:
    • Injection.
    • Oral insertion (oral vaccinations may be broken down in the stomach).
Illustrative background for Primary immune responseIllustrative background for Primary immune response ?? "content

Primary immune response

  • The presence of antigens in the body induces the primary immune response.
  • The antigens are inserted as a dead or weakened pathogen so the vaccine does not give rise to a full-scale infection with symptoms.
Illustrative background for Memory cellsIllustrative background for Memory cells ?? "content

Memory cells

  • The primary immune response leads to the production of memory cells.
Illustrative background for ImmunityIllustrative background for Immunity ?? "content

Immunity

  • Memory cells provide immunity.
  • If the individual is infected by a living pathogen, the memory cells will be ready to induce a fast, strong secondary response.
Illustrative background for Booster vaccinationsIllustrative background for Booster vaccinations ?? "content

Booster vaccinations

  • Booster vaccinations can be given over time to make sure the memory cells are still in the body.
Illustrative background for Continuous trialIllustrative background for Continuous trial ?? "content

Continuous trial

  • Some vaccinations are continuously being changed because the antigens are evolving at a very rapid rate.
  • Pathogens evolve to avoid detection by the immune system. This causes a problem because it makes the vaccines useless.
  • Pathogens with a high mutation rate (e.g. influenza and HIV) are the most difficult to vaccinate against.

Herd Immunity

Herd immunity is the concept that if enough people in a population have immunity against a disease, the entire population are less likely to be infected.

Illustrative background for Spread of a pathogenIllustrative background for Spread of a pathogen ?? "content

Spread of a pathogen

  • Herd immunity works if a large proportion of the population is vaccinated against a disease.
  • If most of the population are immune, the chance of someone without immunity coming into contact with the disease is reduced.
Illustrative background for Population requirementsIllustrative background for Population requirements ?? "content

Population requirements

  • Herd immunity is the basis of widescale vaccination programs.
  • If the disease is highly contagious (e.g. measles), over 90% of the population must be vaccinated.
  • If the disease is less contagious (e.g. polio), over 80% of the population must be vaccinated.
Illustrative background for BenefitIllustrative background for Benefit ?? "content

Benefit

  • Herd immunity offers protection for the most vulnerable people in a population (e.g. new born babies and the elderly).
  • Herd immunity had a major impact on the eradication of smallpox. Herd immunity helped smallpox become eradicated.
Illustrative background for Difficulties with vaccinesIllustrative background for Difficulties with vaccines ?? "content

Difficulties with vaccines

  • Some diseases are harder to vaccinate & eradicate than others.
  • Vaccines for TB are not 100% effective. It's also difficult to deliver the vaccine to poor communities who need it most.
  • Measles has not been eradicated due to poor vaccine uptake. This occurred following a fabricated link between the vaccine and autism.
  • The malaria vaccine requires four shots and is not 100% effective. Not all patients return for all four shots.
  • Cholera is easily treatable with fluid replacement and antibiotics. The vaccine itself produces some sickness, so is avoided.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

Unlock your full potential with Seneca Premium

  • Unlimited access to 10,000+ open-ended exam questions

  • Mini-mock exams based on your study history

  • Unlock 800+ premium courses & e-books

Get started with Seneca Premium