topic 2: vaccines & immunity Flashcards
what do vaccines contain?
antigens derived from pathogenic organisms
what happens to the immune response as a result of vaccines?
when a person comes into contact with that microorganism again, the secondary response will be rapid and the person is unlikely to develop that disease
a vaccine leads to the production of antibodies against a pathogen. How?
- the vaccine contains the antigen from the pathogen
- phagocytes present antigens on their surface
- T Helper cells with a complementary receptor protein bind to the antigen
- TH cells stimulate b cells with complementary antibodies on their surface
- B cells form plasma cells, which produce large amounts of the same antibody
what are the 2 types of vaccine?
live/attenuated
killed/dead/inactivated
what are live/attenuated vaccines?
contain viruses that have been weakened, but not destroyed in a laboratory
example of a live/attenuated vaccine
MMR
what is a killed/dead/inactivated vaccine?
contains viruses that have been destroyed with chemicals or heat
example of a dead/inactivated vaccine
flu vaccine
2 types of immunity
active
passive
what is active immunity?
develops when a person is exposed to microorganisms or foreign substances and the immune system responds
what is passive immunity?
acquired when antibodies are transferred from one person to another
the recipient doesn’t make the antibodies themselves, and the effects only last as long as the antibody is present
give an example of passive immunity
from the mother to baby via placenta or milk
the antibodies that a baby receives via the placenta will eventually be destroyed by the baby’s immune system
how is active natural immunity acquired?
by contracting the disease and suffering the symptoms
what is the duration of active natural immunity?
long lasting
memory b and memory t cells are made
how is active artificial immunity acquired?
vaccines with dead or weakened microbe
what is the duration of active artificial immunity?
long lasting
memory B and T cells made
how is passive natural immunity aquired?
antibodies across the placenta to the fetus or breast milk to the baby
what is the duration of passive natural immunity?
short lived - no memory cells made
maternal antibodies are recognised as antigens and are destroyed by fetal lymphocytes
how is passive artificial immunity acquired?
vaccines with antibodies
used for Rabies, anti-D for rhesus negative mothers
what is the duration of passive artificial immunity?
short lived- no memory cells made
compare passive and active immunity
-active involves memory cells, passive doesnt
-antibodies are produced by plasma and memory cells in active, they are introduced from outside the body in passive
- active is long term because the antibody is produced in responce, passive is short term because antibody is broken down
- active can take time to develop, passive is fast acting
give 6 features of a successful vaccination programme
- suitable vaccine- economically available/in sufficient quantity
- few side effects
- the means to produce,store and transport it
- trained staff to administer it
- public awareness
- try to vaccinate the majority of the population at one time
why is it important in a vaccination programme to try and vaccinate the majority of the population at one time?
to interrupt transmission of the pathogen- herd immunity
what is herd immunity?
the percentage cover or proportion of individulas who must be immune to a disease in order to prevent an epidemic?
what is the importance of herd immunity?
if enough of the ‘herd’ is protected by the vaccine, the disease can only affect isolated individuals so cant spread
the chance of coming into contact with an infected person is reduced
what happens if fewer people are vaccinated?
once vaccine level drops, more individuals will contract the disease and transmit to other unprotected individuals
recently the lack of uptake of MMR vaccine has lead to outbreaks of measles in london because of a fall in % cover
polio epidemics can be prevented by what % cover?
70
influenza epidemics can be prevented by what % of cover
90-95
give 4 possible reasons as to why vaccines dont necessarily eliminate disease
- may not work for people whos immune system doesnt function properly
-some pathogens mutate frequently- antigenic variability - individual may develop disease immediately after vaccination and pass it on
individuals may object for religious, ethical or medical reasons
give some ethical considerations regarding vaccine programmes
- side effects may have LT harm
- should vaccination be compulsory?
- who should vaccines be tested on?
-production/development of new vaccines often involves animals
-should an expensive vaccine program be undertaken if the disease is nearly eradicated?
