VaccinationSpec 4.3.1.7
In short
Vaccination is introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate white blood cells to produce antibodies. If the same pathogen re-enters the body, the white blood cells respond quickly with the correct antibodies, preventing infection. If a large proportion of the population is immunised, the pathogen cannot spread easily.
Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body. This stimulates the white blood cells to produce antibodies.
How it protects an individual
- A vaccine containing dead or inactive pathogen is given.
- The white blood cells are stimulated to produce antibodies.
- If the same pathogen re-enters the body later, the white blood cells respond quickly to produce the correct antibodies.
- The pathogen is destroyed, preventing infection and illness.
How it protects a population
If a large proportion of the population is immunised, the pathogen cannot spread easily because most people it reaches are protected. People who have not been vaccinated are less likely to come into contact with an infected person. This is sometimes called herd immunity.
Evaluating the global use of vaccination
You may be given data, such as the number of cases of a disease against the percentage of people vaccinated, and asked to evaluate. Describe the trend, then link it to the idea above: more people vaccinated means fewer cases.
- Benefit: prevents illness in individuals and reduces the spread of disease through the population.
- Benefit: protects even people who have not been vaccinated, if enough people are immunised.
- Limitation: it is only effective if a large proportion of the population is immunised.
- Limitation: if the proportion of people vaccinated falls, the disease can spread again and cases rise.
To find the percentage of a population vaccinated, divide the number vaccinated by the total population and multiply by 100.
Percentage vaccinated
In a town of 8000 people, 6800 have been vaccinated. Calculate the percentage of the population that is vaccinated.
- number vaccinated ÷ total population = 6800 ÷ 8000 = 0.85
- 0.85 × 100 = 85
Answer: 85%
A vaccine contains dead or inactive pathogen, not active pathogen. It does not contain antibodies, because the white blood cells make them.
You do not need to know vaccination schedules or the side effects of specific vaccines.
Written and checked against the AQA GCSE Combined Science (8464) specification · Updated October 2026