Immunity and vaccines Flashcards
Why do we use vaccines?
To prevent suffering from symptoms of a disease.
Do vaccines always contain pathogens?
No. Antigens can be attached to a dead or attenuated (weakened) pathogens, but in some vaccines they are free.
What is active immunity?
when your immune system makes its own antibodies after being stimulated by an antigen. There are 2 types:
natural - when you become immune after catching the disease artificial - when you become immune after you’ve been given a vaccination containing a harmless dose of the antgen.
What is passive immunity?
- immunity you get from being given antibodies made fromm a different organism - your immune system dosen’t produce any antibodies.
2 types:
- natural: breatmilk or placenta
- artificial: injected with antibodies e.g. if you contract tetnus you can be injeted with antibodies against the tetnus toxin, collected from blood donations.
Characteristics of active immunity?
Active:
Requires exposure to antigen
It takes a while for the protection to develop
Memory cells are produced
Protection is long-term as active immunity involves the production of memory cells specific to a particular antigen. This means the immune system can produce a secondary immune response if the same antigen is deteced again.
Characteristics of passive immunity?
Dosen’t require exposure to antigen
Protection is immediate
Memory cells aren’t produced
Protection is short-term as the antibodies given are broken down/ memory cells aren’t produced so the immune system can’t mount a secondary immune response.
It normally takes 14 days for immunity to develop after recieving a vaccine. Explain why vaccines do not usually offer immediate protection against the disease.
It takes the body time to produce antibodies/memory cells against the antigens in the vaccine.
Explain how vaccination provides immunity.
Vaccines introduce the antigens of a specific pathogen into the body. This causes the body to produce memory cells for that pathogen, without the pathogen causing disease. After vaccination the immune system has the ability to respond quickly to an infection by the pathogen - so the person is immune.
Describe the concept of herd immunity in terms of vaccination.
Herd immunity means that through the vaccination of a significant number of the population, those not vaccinated are also less likely to catch the disease. This is because the reduced occurrence of the disease means that there are fewer people to catch it from.
7) Chickenpox is an infection caused by the varicella zoster virus. It’s possible to prevent chickenpox by vaccination with antigens from the virus or by injection of preformed antibodies against the virus.
Compare how the effects of these two prevention methods would differ.
For injection with the vaccine it would take a while for protection to develop, whereas protection would be immediate if antibodies were used. However, unlike injection with antibodies, vaccination would stimulate the production of memory cells. This means that protection is long-term, whereas the injected antibodies would break down meaning they would only provide short-term protection.
