Principles of immunisation Flashcards
Describe the principles of active immunity.
Active immunity can be natural (exposure/infection) or artificial (vaccination).
Describe active immunity acquired through exposure/infection.
The antigen (part of or whole organism) stimulates an immune response.
Gives long-term immunity, and immunological memory.
No immediate effect but faster and better response to next antigenic encounter.
Describe active immunity acquired through vaccination or immunisation.
Define “vaccination”.
Vaccination is the administration of antigenic material (a vaccine) to stimulate an individuals immune system to develop adaptive immunity to a pathogen.
Describe vaccination where the whole organism is killed.
There is a target organism. (e.g. polio).
This kind of vaccine is effective and relatively easy to manufacture.
Booster shots likely required.
Virus must be heat killed effectively - any live virus can result in vaccine-related diseases.
Describe vaccination where the whole organism is attenuated.
(Used mainly in viruses).
A live avirulent strain of target organisms is isolated. This type of vaccine can be very powerful and long-lasting.
They stimulate natural infection (produce antibodies and memory cells).
They must be kept cool (don’t travel well) - cold chain network.
Shouldn’t be used in pregnant or immunocompromised patients.
Describe the attenuation mechanism.
The pathogenic virus is isolated from a patient and grown in human cultured cells.
The cultured virus is then used to infect monkey cells.
The virus acquires many mutations that allow it to grow well in monkey cells (i.e. it adapts to the new species)
The virus no longer grows well in human cells (it is attenuated) and can be used as a vaccine - as it is less able to target humans.
Describe sub-unit vaccines.
Sub-unit vaccines use different pieces of the microorganism. So the body should ideally have a string immune response targeted to these key parts.
However, they are not very immunogenic without an effective adjuvant (enhance the response - e.g. if there is only a little of the pathogen present).
For usage, the generation of immunity must be understood.
Name some parts of diseases that sub-unit vaccines are used against.
Hepatitis B surface antigen (HBsAg).
Human papilloma virus proteins.
Describe a toxoid vaccine.
The toxin is treated with formalin.
Toxoid retains antigenicity but has no toxic acitivity - can induce an immune response, but only against the toxin not the organism that produces it (e.g. tetanus, disphtheria).
Define “toxoid”.
A toxoid is a chemically modified toxin from a pathogenic microorganism, which is no longer toxic but is antigenic and can be used as a vaccine.
Describe some temporary contra-indications of vaccination.
Febrile illness.
Pregnancy - cannot be given live attenuated vaccines.
Describe some permanent contra-indications of vaccination.
Allergy
Immunocompromised - cannot be given live attenuated vaccines as individuals may develop disease from the vaccine strain.
Describe the concept of herd immunity.
The primary aim of vaccination is to protect the individual who receives vaccination.
Vaccinated individuals are less likely to be a source of infection to others
=Reduces the risk of unvaccinated individuals being exposed to infection.
Describe some immunological factors that make a vaccine more effective.
Potent antibody response - high antibody titers.
Potent CD8+ cytotoxic T cell response.
CD4+ T helper response (this is induced by all vaccines).
Memory.
