This definitions covers Key Definitions within Vaccination and Herd Immunity for GCSE Biology. How vaccines work, types of vaccines, population immunity, vaccination programs It is section 9 of 14 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 9 of 14
Practice
18 questions
Recall
21 flashcards
Key Definitions
Vaccination: The process of introducing antigens into the body (via injection or oral administration) to stimulate the immune system to produce memory cells, providing protection against future infection without causing disease.
Vaccine: A preparation containing antigens from a pathogen (dead, attenuated, or as components) that triggers an immune response and memory cell formation when administered.
Herd immunity: Protection of unvaccinated individuals within a population because a sufficiently high proportion of the population is immune, preventing the pathogen from spreading and reaching vulnerable people.
Herd immunity threshold: The minimum proportion of a population that must be immune for herd immunity to be achieved. Calculated as 1 - (1/R₀), where R₀ is the basic reproduction number.
Live attenuated vaccine: A vaccine containing weakened (but living) pathogen that can replicate briefly without causing disease. Produces strong, long-lasting immunity (e.g., MMR vaccine).
Inactivated vaccine: A vaccine containing killed pathogens or pathogen components. Safer for immunocompromised individuals but may require booster doses (e.g., flu vaccine, hepatitis A).
Booster dose: An additional vaccine dose given some time after the initial course to maintain or enhance immunity by restimulating memory cells and increasing antibody levels.
Basic reproduction number (R₀): The average number of new cases one infected individual causes in a fully susceptible population. A higher R₀ means more contagious and a higher vaccination threshold needed for herd immunity.