Vaccination (AQA GCSE Combined Science: Trilogy: Biology): Revision Note

Why vaccinate?

• Vaccination will prevent illness in an individual by providing artificial immunity

• Vaccination involves exposing an individual to the antigens of a pathogen in some form, triggering an immune response which results in the formation of memory cells which can make antibodies against it

• If a vaccinated individual is infected with the pathogen, they can destroy it before they become infectious

• Consequently, vaccines reduce the likelihood that an infected individual will spread the pathogen they have been vaccinated against to others

• If a large number of the population are vaccinated, it is unlikely that an unvaccinated individual will become infected with the pathogen

• This is the principle behind the idea of herd immunity

• There are three main scenarios with vaccination:

  • There are no vaccinations and the disease spreads quickly

  • Some of the population are vaccinated and the disease spreads to fewer people

  • Most of the population are vaccinated and this prevents the spread

Use this image

Worldwide vaccination

• The role of the WHO is to monitor global diseases: it tracks whether diseases are endemic, epidemic or pandemic

• The importance of vaccines cannot be overstated:

  • The number of people with measles worldwide is increasing due to a drop in the vaccination rate globally

  • There was some controversy over the MMR vaccine in 1998 and the number of vaccinations dropped significantly after this

• Vaccines have reduced drastically the cases of diseases worldwide

Vaccination statistics table

Data source: ourworldindata.org/vaccination (opens in a new tab)

Advantages and disadvantages of vaccinations

Advantages:

• Diseases that were once common are now fairly rare due to widespread vaccinations (for example polio, measles)

• Epidemics can be prevented if a large number of the population are vaccinated

Disadvantages:

• The vaccine doesn’t always give immunity

• There can be side effects to the vaccine, for example swelling or a rash to more severe reactions such as seizures

How do vaccines work?

• Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies

• If the same pathogen re-enters the body the white blood cells respond quickly to produce the correct antibodies, preventing infection

Use this image

• There are two types of immunity:

  • Active immunity that comes from the body creating antibodies to a disease either by exposure to the disease (natural) or by vaccination (artificial)

  • Passive immunity that comes from antibodies given from another organism, for example in breast milk

• With the measles vaccine, for example, vaccination with a weakened form of the measles virus results in the production of antibodies and memory cells

• When exposed to the virus naturally and infected, an individual can produce a higher concentration of antibodies much more quickly to destroy it

Graph of the effect of vaccination on antibody production

Use this image