What is immunity and what are the 2 types of immunity?
The ability to be resistant to infection.
1) Passive
2) Active
What is passive immunity?
- It is the immunity that is produced by introducing antibodies to an individual from an outside source.
- No direct contact with the pathogen or antigen is needed and the immunity is applied immediately.
- As antibodies are not produced by the body itself, they are not replaced when they are broken down and no memory cells are formed, while there’s also no lasting immunity.
e. g. the anti-venom gave when bitten by a snake.
What is active immunity?
- Produced by stimulating the production of antibodies by the individual’s own immune system.
- Direct contact with pathogen or antigen is needed.
- Immunity takes time to develop and generally long lasting.
What are the 2 types of active immunity?
- Natural active immunity - happens when an individual becomes infected with a disease under normal conditions and the body will continue to reproduce its own antibodies for many years.
- Artificial active immunity - forms the basis of vaccination, where it involves stimulating an immune response without them suffering from the symptoms of the disease.
What is vaccination and what’s the point?
Vaccination is the introduction of a disease antigens into the body, either by injection or by mouth and it is to stimulate an immune response.
The material injected is a vaccine.
What’s the point of injecting a vaccine?
Although it stimulates a slight response because it’s a small amount but it produced memory cells which will allow a greater and more immediate response to a future infection of the same pathogen.
What features are needed for a successful vaccination?
- Must be economically available and enough quantities for most of the vulnerable populations.
- Fewest side effects because unpleasant side effects would discourage individuals from a population to be vaccinated.
- Means of producing, storing and transporting the vaccine must be available. (technologies, hygienic conditions and refrigerated transport).
- Administrating the vaccine properly e.g. skilled professionals.
- It must be able to vaccinate the vast majority of the vulnerable population to produce herd immunity.
What is herd immunity?
When the majority of the population has been vaccinated so it would be difficult for the pathogen to spread within the population so those who are not vaccinated can be protected by keeping everyone else immune.
Why is herd immunity important?
Because it’s impossible to vaccinate every single person within the population. e.g. babies cannot be vaccinated because their immune system is not yet fully functional.
It could also be dangerous to vaccinate those who are ill.
How can herd immunity be achieved?
A large percentage of the population must be vaccinated to enable herd immunity.
Also, vaccination must be carried out at one time with the majority population. This means that for a period of time, there are very few individuals in the population with the disease and the transmission of the pathogen is interrupted.
Why vaccination may not eliminate a disease?
- Vaccination might fail to stop immunity e.g. people with defective immune systems.
- Individuals might develop the disease immediately after the vaccination before their immunity levels are high enough to prevent it so they might reinfect others.
- Pathogens might mutate so its antigens will change and the vaccines would become ineffective because new antigens on the pathogen are no longer recognised by the immune system so it cannot produce antibodies to destroy the pathogen. (This is called antigen variability).
- There are so many varieties of pathogens so it’s hard to develop a vaccine that is effective against them all.
- Certain pathogens ‘hide’ from the body’s immune system, either by concealing inside a cell or living at a place out of reach.
- Individuals might reject due to religious, ethical, medical reasons.
