Immunity and Vaccines 2C Flashcards
What can help prevent a disease
A vaccine
What do vaccines contain, and what do they do?
Vaccines contain antigens, which produce memory cells, against a particular pathogen without causing disease this means that you become immune without causing symptoms, these antigens may be free or attached to a dead or attenuated (weakened) pathogen
Define herd immunity
Vaccine protect individuals that have had them, and because they reduce the occurrence of the disease, the people who are not vaccinated are also less likely to catch the disease because there are less people to catch it from
How are vaccines administered
They are injected into the muscle or administered orally
What are the disadvantages of an oral vaccine
It could be broken down by enzymes in the gut or the molecules of the vaccine may be too large to be absorbed into the blood
What do booster vaccines do?
Ensure that memory cells are being produced
What does antigenic variation do
Helps some pathogens evade the immune system
What do antigens do
Activate the primary response
When is the secondary response stimulated
When you’re infected for a second time with the pathogen
Define genetic variation
When a pathogen changes their surface antigens so when you are infected for a second time the memory cells will not recognise the different antigens so the immune system starts again with primary response, this could be due to mutations
Examples where antigenic variation could take place
HIV and influenza virus
How does antigenic variation affect the production of vaccines to prevent people catching influenza virus
The flu vaccine changes every year , this is because the antigens on the surface of the influenza virus change regularly forming new strains of the virus
Memory cells will not recognise the antigens of the new strain. The strains are immunologically distinct
This is why a new vaccine needs to be made every year so that they are most effective
Describe active immunity
when your immune system makes its own antibodies
Define natural active immunity
When you become immune after catching a disease
Define artificial immunity
When you become immune after being given a vaccine containing a harmless dose of an antigen