Vaccination (AQA GCSE Biology: Combined Science)

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

Herd immunity protects the vulnerable that may not be able to have the vaccine

Worldwide vaccination

• The role of the WHO is to monitor global diseases, they will track if a disease is endemic, epidemic or pandemic
• The importance of vaccines cannot be underestimated:
  • The number of people with measles worldwide is increasing even though there is a vaccine
  • The increase is 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

Advantages & disadvantages of vaccination table

• 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

The process of long-term immunity by vaccination

• 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 to you 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 showing the number of measles antibodies in the blood following vaccination and infection