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
2 difficulties surrounding mass vaccination
poverty in developing world
rejection of a percentage of the population in the developed world
when does a persons vaccination schedule usually begin in the UK?
2 months
5 vaccinations you receive in the UK
influenza
whooping cough
tetanus
poliomyelitis
diphtheria
why might herd immunity be compromised in developed countries?
if parents believe adverse publicity and refuse to have their children vaccinated
what happens within a population of pathogenic microorganisms?
new strains arise continuously by mutation
what are the new strains described as showing and why?
antigenic variation
if they have antigens on their surface that are different from the original strain
what are the new strains of pathogens showing antigenic variation said to be and why do they work?
genetically and immunologically distinct from parent strain
succeed as it employs a selective advantage
what effect do new antigens have on the influenza virus?
enable it to avoid effects of the human body’s immunological memory
how do new antigens disabling immunological memory allow influenza reinfect a person?
new antigens are not recognised by their memory cells
