How Vaccines Work (Cambridge (CIE) AS Biology): Revision Note

How vaccines work

• A vaccine is a suspension of antigens that are intentionally put into the body to induce artificial active immunity 

  • A specific immune response where antibodies are released by plasma cells

• There are two main types of vaccines:

  • Live attenuated

  • Inactivated

• Vaccines are administered either by injection or orally (by mouth)

  • When a person is given a vaccine they have been given a vaccination (they are said to have been vaccinated)

• The vaccinations given by injection can be into a vein or muscle

• Vaccinations produce long-term immunity as they cause memory cells to be created

  • The immune system remembers the antigen when reencountered and produces antibodies to it, in what is a faster, stronger secondary response

Live attenuated vaccines

• Live attenuated vaccines contain whole pathogens (e.g. bacteria and viruses) that have been ‘weakened’

  • These weakened pathogens multiply slowly allowing for the body to recognise the antigens

  • They trigger the primary immune response (plasma cells to produce antibodies)

  • These vaccines tend to produce a stronger and longer-lasting immune response

Inactivated vaccines

• Inactivated vaccines contain whole pathogens that have been killed (‘whole killed’) or small parts (‘subunit’) of the pathogens (e.g. proteins or sugars or harmless forms of the toxins – toxoids)

  • As inactivated vaccines do not contain living pathogens they cannot cause disease, even for those with weak immune systems

  • However these vaccines do not trigger a strong or long-lasting immune response like the live attenuated vaccines

    • Repeated doses and / or booster doses are often required