13 Communicable diseases Flashcards
what is vaccination?
deliberate exposure of an individual to antigens from a foreign source in order to provoke an immune response and provide immunity
(i.e. artificial active immunity)
why does a vaccination work to prevent development of symptoms from infection?
generates a primary immune response and stimulates memory cells
∴ in future faster secondary response will occur following infection
what is a live attenuated vaccine? what is a strength and
a limitation of it?
modified strains of bacteria/viruses that can multiply BUT are not pathogenic
+ strongest response and ∴ long-lasting immunity
- cannot be given to people with compromised immune systems
what is a killed-inactivated vaccine? what is a strength and a limitation of it?
bacteria/virus is killed with chemical treatment, but antigens remain intact, provoking an immune response
+ more stable than live-attenuated, and does not require refrigeration
- provokes weaker immune response ∴ booster(s) needed
what is a toxoid vaccine? what is a strength and a limitation of it?
toxoids are extracted and treated with formaldehyde to prevent symptoms –> triggers immune response and production of antitoxins
+ safe when toxins are reason for virulence
- does not give a strong immune response
what is a subunit vaccine? what is a strength of it?
only specific antigens extracted and used
+ can construct vaccines for several strains
what is an artificial antigen recombinant vector? what is a strength of it?
genes coding for the antigens of the pathogen are transferred through genetic engineering to harmless microorganisms
+ provides immunity to agents that can’t easily be attenuated without destroying antigen activity
what is the aim of a vaccination programme?
to protect the population from a wide range of disease
why are boosters used?
to increase the number of memory cells
increases speed of secondary immune response to destroy pathogen before it can cause disease
how are vaccines used to prevent epidemics?
reducing chance of transmission
by increasing herd immunity
what is ring vaccination?
a vaccination ring around the geographical centre of an epidemic to prevent its spread
give three advantages of vaccination programmes
few/no side effects
economically viable for the whole population
easy to produce, transfer and store
how can the mutation of a pathogen prevent a vaccine being effective?
change in genetic material causes change in antigens/glycoproteins
∴ previous vaccine no longer has complementary antibody ∴ cannot bind to antigen
how can surface antigen variation prevent a vaccine being effective?
difficult to target all different antigens (especially if high mutation rate)
different strains in different geographical locations
give three biological problems in implementing vaccines
live-attenuated pathogen could mutate and become virulent
storage/transport/distribution can be expensive if refrigeration is required
low nutritional state of target population may have weakened their immune systems