Vaccines

How they work

• antigen binds to receptor on B cell

• B cells into activated/stimulated by T cell (cytokines)

• B cell divides by mitosis/clonal selection

• plasma B cells release antibodies

• memory B cells formed

• if future contact with pathogen, memory B cells produce antibodies at faster rate and in much higher quantities

Herd Immunity

• sufficiently large proportion of pop. vaccinated so hard for pathogen to spread.

• based on idea that pathogens are spread when individuals are in close contact

• individuals who aren’’t immune are still protected

• important because you can’t vax everyone i.e young children/babies aren’t because their immune system isn’t fully functional → also dangerous to vax ill/people with compromised immune systems

Why vax might not eliminate disease

• fails to induce immunity in certain individuals

• ppl may develop disease right after vax

• pathogen may mutate freq. so antigens change so vax becomes ineffective as new antigens not recognised by immune system

• too many varieties of path. to vax against all

• certain path. hide from immune system i.e cholera

• ppl may reject for religious, ethical or medical reasons