3.1.7: Vaccination
Not started yet — this one needs some love.
Vaccination: introduces dead or inactive pathogens (which display antigens) into the body.
Immune response: lymphocytes recognise the antigens on dead/inactive pathogens → produce specific antibodies to match those antigens.
Memory cells are formed → if the same pathogen re-enters, lymphocytes respond rapidly and produce the correct, specific antibodies quickly → infection is prevented before symptoms develop.
Herd immunity: if a large proportion of the population is vaccinated, the pathogen cannot spread easily — even unvaccinated individuals are protected (fewer susceptible hosts to infect).
Key point: vaccines contain antigens (from dead/inactive pathogens), NOT pre-made antibodies; your body MAKES the antibodies in response.
Common exam mistakes
Vaccines contain antigens (from dead/inactive pathogens), NOT antibodies — a very common misconception. The vaccine triggers your body to produce antibodies; it does not provide them.
Lymphocytes produce the antibodies — not the 'body', 'immune system' or 'white blood cells' (too vague). Must specify lymphocytes for full marks.
Must say the antibodies produced are specific to the pathogen — just saying 'antibodies are produced' lacks the crucial word 'specific'.
On re-infection with the same pathogen, antibodies are produced more rapidly AND in greater quantity — both speed AND quantity matter.
Must explain what the antibodies do: bind to antigens on the pathogen's surface AND mark it for destruction, or neutralise toxins — not just 'are produced' or 'help'.
Antigens are on the pathogen's surface; antibodies bind to antigens. The vaccine introduces antigens; your body produces antibodies in response — these are DIFFERENT things.
Memory cells are NOT antibodies — they are immune cells that 'remember' the antigen and respond quickly on re-exposure. Do not confuse memory cells with either antibodies or antigens.