Vaccines (AQA A Level Biology): Revision Note

Vaccines

• Vaccines introduce pathogenic antigens into the body, triggering a specific immune response which results in the release of antibodies by plasma cells

  • Vaccines can contain:

    • weakened forms of the pathogen

    • antigens

    • genetic material that codes for the antigens

• Vaccinations produce active immunity, as they cause memory cells to be produced

  • The immune system recognises the antigen and triggers a faster, stronger secondary response

  • This response eliminates the pathogen before symptoms develop

Herd Immunity

• Vaccines protect individuals and populations from disease by triggering immunity

• Herd immunity occurs when enough people are vaccinated to stop the spread of infection

• This protects unvaccinated individuals, such as babies or those with weakened immune systems

• The more infectious a disease is, the higher the proportion of the population that must be vaccinated

• If vaccination rates drop below the threshold, herd immunity is lost (e.g. measles outbreak in Swansea, Wales, 2012)