CELLS: Vaccines and Immunity

Question 1

What is immunity?

Answer 1

The ability of an organism to resist infection.

Question 2

What are the two forms of immunity?

Answer 2

Passive and active.

Question 3

What is passive immunity?

Answer 3

Type of immunity produced by the introduction of antibodies into individuals from an outside source - the immune system doesn’t produce antibodies of its own.

Question 4

What isn’t needed for passive immunity to occur?

Answer 4

Direct contact with the pathogen or its antigen.

Question 5

What type of protection is given by passive immunity?

Why is this?

Answer 5

Only gives short term protection - no lasting immunity.

As the body hasn’t produced the antibodies itself, no memory cells have formed and antibodies are broken down after initial use.

Question 6

What are the two types of passive immunity?

Answer 6

Natural and artificial.

Question 7

Give an example of natural passive immunity:

Answer 7

A baby becomes immune due to the antibodies it receives from its mother, through the placenta and the breastmilk.

Question 8

Give an example of artificial passive immunity:

Answer 8

Anti-venom given to the victims of snake bites.

After contracting tetanus, being injected with antibodies against the toxin, collected from blood donations.

The immunity comes after being injected with the antibodies from someone else.

Question 9

What is active immunity?

Answer 9

Type of immunity produced by stimulating the production of antibodies by the individuals’ own immune system.

Question 10

What are the two types of active immunity?

Answer 10

Natural and artificial.

Question 11

What is required for active immunity?

Answer 11

Direct contact with the pathogen or its antigen is necessary.

Question 12

What type of protection is given by active immunity?

Why is this?

Answer 12

Long lasting protection.

This is because the individuals’ own immune system has created antibodies, as well as memory cells, meaning antibodies are produced when complementary antigens are present in the blood again.

Question 13

Give an example of natural active immunity:

Answer 13

An individual becoming infected with a disease under normal circumstances.

The body produces its own antibodies and may continue to do so for many years.

Question 14

What are the key differences between active and passive immunity?

Answer 14

• Active immunity requires exposure to the antigen, whereas passive immunity does not.
• In active immunity it takes a while for protection to develop, whereas in passive immunity protection is immediate.
• In active immunity memory cells are produced, whereas in passive immunity they are not.
• In active immunity protection is long-term, whereas in passive immunity protection is short-term.

Question 15

What is vaccination?

Answer 15

The introduction of the appropriate disease antigens into the body, either by injection or by mouth.

Question 16

What is the aim of vaccination?

Answer 16

The intention is to stimulate an immune response against a particular disease.

Question 17

What do vaccinations contain?

Answer 17

Antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease.

This means you become immune without getting any symptoms.

Question 18

What is herd immunity?

Answer 18

When a sufficiently large proportion of the population has been vaccinated making it difficult for a pathogen to spread within the population, meaning those who are not immune are still protected.

Question 19

Why is herd immunity important?

Answer 19

It is never possible to vaccinate everyone in a large population, such as babies and very young children and those who are ill/have compromised immune systems.

Question 20

Why are babies and very young children not vaccinated?

Answer 20

Their immune system is not yet fully functional.

Question 21

What type of antigens are found in vaccines?

Answer 21

• Free antigens.
• Attached to a dead or attenuated pathogen.

Question 22

What is an attenuated pathogen?

Answer 22

A weakened pathogen.

Question 23

What is a disadvantage to taking a vaccine orally?

Answer 23

• Could be broken down by enzymes in the gut.
• Molecules of vaccine may be too large to be absorbed into the blood.

Question 24

Why are booster vaccines sometimes given?

Answer 24

To ensure memory cells are being/have been produced.

Question 25

What is the benefit of having memory cells?

Answer 25

They remain in the blood and allow a greater, and more immediate response to a future infection with the pathogen.

So, new infection is rapidly overcome before it can cause any harm and with few, if any symptoms.

Question 26

What do antigens on the surface of pathogens activate?

Answer 26

The primary immune response.

Question 27

List factors of a successful vaccination programme:

What makes these factors possible?

Answer 27

• Economic availability of suitable vaccine - must be sufficient quantities to immunise the most vulnerable of the population.
• Few side-effects - unpleasant side-effects may discourage individuals from being vaccinated.
• Available means of producing, storing and transporting vaccine - usually involves technologically advanced equipment, hygenic conditions and refrigierated transport.
• Must be means of administering vaccine properly at appropriate time - involves training staff with skills at different centres throughout the population.
• Must be possible to vaccinate the vast majority of the vulnerable population to produce herd immunity.

Question 28

There are 6 things to consider.

Why might it be difficult to eradicate a disease, even when the criteria for successful vaccination are met?

Answer 28

• Vaccination fails to induce immunity in certain individuals, eg. those with defective immune systems.
• Individuals may develop the disease immediately after vaccination but before their immunity levels are high enough to prevent it.
• Antigenic variability.
• May be many varieties of pathogen that its almost impossible to develop a vaccine that is effective.
• Pathogens may ‘hide’ from immune system, either by concealing themselves inside cells, or by living in places out of reach.
• Individuals may have religious, ethical or medical objections to vaccination.

Question 30

What is antigenic variation?

Answer 30

Where the genes of a pathogen mutate, causing the antigens on the surface of the pathogen to change.

Question 31

How does antigenic variation have implications on vaccinations?

Answer 31

• The pathogen mutates, changing the antigens suddenly and not gradually.
• So, vaccines become inneffective because new antigens on the pathogen are no longer recognised by memory cells in immune system (produced from vaccination).
• As a result, immune system does not produce antibodies to destroy the pathogen - immune system must start again and carry out a primary response against new pathogens.

Question 32

Explain how antigenic variation affects the production of vaccines to help people prevent catching influenza:

Answer 32

• Influenza virus changes every year - as antigens change regularly forming new strains of virus.
• Memory cells produced from vaccination with one strain of the flu will not recognise other strains with different antigens.
  
  • As strains are immunologically distinct.
• Each year, different strains are in circulation and so a different vaccine has to be made.
• New vaccines are developed and one is chosen every year that is the most effective against recently circulating strain.
• Governments and health authorities then implement a programme of vaccination using the most suitable vaccine.

Question 33

Describe some ethical issues surrounding vaccinations:

Answer 33

• Development and production often uses animals.
• Side-effects can sometimes cause long-term harm.
• Vaccine testing on human participants to determine safety.
• Trialing vaccines with unknown health risks only in a country where targeted disease is common/where people are most vulnerable.
• Compulsory vaccinations to ensure they are fully effective - should people be able to opt out? On what grounds?
• Balancing individual health risks against the advantages of controlling a disease for the benefit of the whole population.