3.7- immunisation Flashcards
what is immunisation?
process where a person develops immunity to a disease-causing organism
what is active immunity?
the protection gained as a result of the person’s body producing its own antibodies
how does a person gain immunity by natural means?
through immunological memory
if initial exposure to an infection is survived, subsequent exposure to the same antigen at a layer date results in the secondary response, preventing the disease from recurring
what does a vaccine use?
uses antigens from infectious pathogens to create memory cells
what can the antigens used in a vaccine be?
inactivated pathogen toxins
dead pathogens
parts of pathogens
weakened pathogens
3 ways vaccines are introduced into the body
injection
ingestion
nasal spray
what is an antigen usually mixed with?
adjuvant
what is an adjuvant?
chemical substance
what 2 things does the changed antigen cause in each vaccination case?
production of B and T cells
the formation of antibodies but does not cause the disease
what do some B and T cells persist in the body as and what do they do?
memory cells
initiate secondary response if person is exposed to the normal disease-causing antigen at a later date
when does herd immunity occur?
when a large percentage of the population is immunised
how are non immune individuals protected in herd immunity?
there is a lower probability they will come into contact with infected individuals
disrupts normal chain of infection
what makes herd immunity effective?
only a minority of the population can be left unvaccinated
what is the herd immunity threshold?
the percentage of immune individuals in a population above which a disease no longer manages to persist
3 factors that alter the value of the herd immunity threshold
virulence of pathogen (capacity for causing disease)
vaccines effectiveness
density of population