Vaccination and Immunisation — AQA GCSE Biology
Vaccination protects people from communicable diseases by preparing the immune system in advance.
How vaccination works
A vaccine contains small quantities of dead or inactive forms of a pathogen (or its antigens). When injected:
- The white blood cells (lymphocytes) recognise the antigens and produce antibodies.
- Memory cells remain in the body.
- If the real pathogen later enters, the immune system responds quickly and produces antibodies in large numbers, destroying the pathogen before the person becomes ill.
Herd immunity
If a large proportion of the population is vaccinated, the spread of a pathogen is greatly reduced. This protects even those who are not vaccinated, because the pathogen cannot spread easily. This is herd immunity.
Evaluating vaccination
- Benefits: prevents illness and death; can control or even eradicate diseases (e.g. smallpox).
- Drawbacks: rare side effects; vaccines do not always give complete protection.
You should be able to use data to evaluate vaccination programmes.
Exam tips
- A vaccine contains dead or inactive pathogen/antigens.
- Explain the secondary response: faster and larger antibody production on re-exposure.
- Define and explain herd immunity.
- Be ready to evaluate vaccination using given data.