immunity and vaccines

vaccine

contain antigens - free or attached to dead or weak pathogen

injected or taken orally

orally may be broken down by enzymes in gut / vaccine too big to absorb into blood

antigens cause body to produce memory cells, without disease causoing pathogen

u become immune without symptoms / illness

protect the people that take them, but also those that dont

as theres less people to catch it from = herd immunity

booster vaccines given yrs later to make sure memory cells are produced

antigenic variation

antigenic variability/variation = some pathogens change their surface antigens. due to changes in the genes of the pathogen

means if youre infected a second time, the memory cells produced in the forst infection wont recognise the different antigens.

immune system starts from scratch and has to carry out a primary response against new antigens. takes time, so you get ill again!!

how it affects VACCINES

variation makes it difficult to develop vaccines agianst some pathogens. common example - HIV, influenza virus (flu)

flu vaccine changes every year because the antigens on surface of flu are constantly changing. forming new STRAINS of the virus

the strains are IMMUNOLOGICALLY distinct, so memory cells for one wont recognise the antigens for the other one

every yr theres different strain of flu in population so needs a different vaccination

new vaccines are developed and one is chosen every yr that is most effective against the recently circulating flu virus

active immunity - immune system makes i ts own antibodies after stimulation from an antigen

natural = Immunity after catching a disease

artificial = immunity after given vaccination

passive immunity -given antibodies made by different organism. YOUR immune system doesnt produce the antibodies on its own

natural = baby becomes immune due to antibodies received from mother in breast milk and placenta

artificial = immunity after being injected with antibodies from someone else - collected from blood donations

longterm protection - memory cells

short term protection - antibodies broken down

take time for protection to develop

protection is immediate

requires exposure to antigen