2C - Immunity and vaccines

Question 1

How do vaccines work?

Answer 1

They contain antigens that cause your body to produce memory cells against a particular pathogen, without causing disease. This means you become immune without getting any symptoms.

Question 2

What do vaccines do to individuals?

Answer 2

Protect individuals that have had them and, because they reduce the occurence of the disease, those not vaccinated are also less likely to catch the disease - herd immunity.

Question 3

What do vaccines contain?

Answer 3

Antigens - free or attached to a dead or attenuated (weakened) pathogen.

Question 4

How can vaccines be taken?

Answer 4

Orally or by injection.

Question 5

What are the disadvantages of taking a vaccine orally?

Answer 5

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.

Question 6

What can be given later on (several years) after a vaccine and why?

Answer 6

Booster vaccines to make sure that memory cells are produced.

Question 7

What is antigenic variation/antigen variability?

Answer 7

Different antigens are formed due to changes in the genes of a pathogen - some pathogens can change their surface antigens.

Question 8

What are examples of pathogens that show antigenic variation?

Answer 8

HIV and the influenza virus.

Question 9

How does antigenic variation affect the production of vaccines to help prevent people catching influenza?

Answer 9

The influenza (flu) vaccine changes every year because antigens on the surface of the influenza virus change regularly, forming new strains of the virus.

Memory cells produced from vaccination with one strain of the flu will not recognise other strains with different antigens. The strains are immunologically distinct.

Every year there are different strains of the influenza virus circulating in the population, so a different vaccine has to be made.

New vaccines are developed and one is chosen every year that is the most effective against the recently circulating influenza viruses.

Governments and health authorities then implement a programme of vaccination using the most suitable vaccine.

Question 10

What is antigenic variability caused by?

Answer 10

Mutations or horizontal transfer of plasmids containing new genes.

Question 11

What does infection by a new strain of a disease/infection cause?

Answer 11

The primary response to detect it and respond to it.

Question 12

What is active immunity?

Answer 12

The type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen. (Actively triggering primary immune response.)

Question 13

What are the 2 types of active immunity?

Answer 13

Natural

Artificial vaccination

Question 14

What is natural active immunity?

Answer 14

When you become immune after catching a disease so the body produces its own antibodies.

Question 15

What is artificial vaccination (active immunity)?

Answer 15

When you become immune after you’ve been given a vaccination containing a harmless dose of antigen.

Question 16

What is passive immunity?

Answer 16

The type of immunity you get from being given antibodies made by a different organism - your immune system doesn’t produce any antibodies of its own.

Question 17

What are the 2 types of passive immunity?

Answer 17

Natural

Artificial

Question 18

How many types of active immunity are there?

Answer 18

2

Question 19

How many types of passive immunity are there?

Answer 19

2

Question 20

What is natural passive immunity?

Answer 20

When a baby becomes immune due to the antibodies it receives from its mother, through the placenta and in breast milk.

Question 21

What is artificial passive immunity?

Answer 21

When you become immune after being injected with antibodies from someone else.

E.g. If you contract tetanus you can be injected with antibodies against the tetanus toxin, collected from blood donations.

Question 22

What are the differences between active and passive immunity?

Answer 22

Active immunity requires exposure to antigen but passive immunity doesn’t.

It takes a while for protection to develop in active immunity but protection is immediate in passive immunity.

Memory cells are produced in active immunity but they aren’t in passive immunity.

In active immunity, protection is long-term as the antibody is produced (after activation of memory cells) in response to complementary antigen being present in the body but in passive immunity, protection is short-term because the antibodies given are broken down.

Question 23

How does artificial passive immunity work?

Answer 23

When someone has already been infected or is likely to become infected with a pathogen antibodies are extracted from the blood plasma of an infected person. The antibodies assist the body’s normal immune response.

This does not itself lead to long-term immunity.

Question 24

What are the ethical issues surrounding vaccines?

Answer 24

Tested on animals or use animal based substances to produce them.

Testing on humans can be tricky - volunteers placed at unnecessary risk of contracting a disease.

Some people don’t want to take the vaccine due to the risk of side effects but they are still protected because of herd immunity.

If there was an epidemic of a new disease then difficult decisions would have to be made about who should receive the vaccine first.

Question 25

What is herd immunity?

Answer 25

If enough people are immune to a pathogen (>90%) then the remaining people are often protected due to a lack of hosts for the pathogen to reproduce in.