scientific basis of vaccines

Question 1

what is attenuation (in vaccines)

Answer 1

making the pathogen harmless but still alive

Question 2

what is meant by cross-specie protection

Answer 2

similar antigens between pathogens eg antigens of cowpox and smallpox were similar .’. cowpox Ig provide protection against smallpox

Question 3

definition of vaccine

Answer 3

material from an organism that will actively enhance adaptive (acquired) immunity

Question 4

what is meant by herd immunity

Answer 4

if majority is immune, there is a resistance to the spread of contagious disease within population .’. provides measure of protection to those who are not vaccinated

Question 5

what can boost herd immunity

Answer 5

periodic outbreaks of disease in the community

vaccines

Question 6

how do periodic outbreaks of disease in the community boost herd immunity

Answer 6

improves immunological memory .’. with periodic outbreaks people become naturally immune and don’t spread it i the future

Question 7

risks of vaccines

Answer 7

measles vaccine - 1/1000 suffer fever/convulsions.

1/400000 suffer meningo-encephalitis

Question 8

what is active immunity

Answer 8

body’s own B-cells producing antibodies against the antigen and forming memory B-cells that mean there will be a greater response on second exposure.

Question 9

what is passive immunity

Answer 9

short-term immunity that is induced by receiving antibodies from another source eg mother or medication

Question 10

what causes active immunity

Answer 10

Natural exposure to antigen (that is carriage)
Getting infected by the pathogen
Being vaccinated

Question 11

when may we use passive immunity in a clinical setting

Answer 11

for prophylaxis and treatment

Question 12

how long does adaptive immune system take on primary exposure

Answer 12

5-7 days to start antibody response and 2 weeks to reach full response

Question 13

what happens in adaptive immune response to primary exposure

Answer 13

first IgM produced by Bcells then class switch -> IgG (more effective)
some bcells and tcells become memory cells

Question 14

how long does adaptive immune system take on secondary exposure

Answer 14

with memory cells circulating, only takes 2 days to mount full immune response. High affinity IgG produced straight away

Question 15

general principles needed to consider when designing a vaccine

Answer 15

need to induce correct type of response
need to induce immune system in correct place
age when vaccinating
route of inoculation

Question 16

what is meant by vaccine needing to generate correct type of response

Answer 16

depending on pathogen we may want humoral or cell mediated response

Question 17

what is meant by vaccine needing to generate response in correct place

Answer 17

diff pathogens reside in diff parts of the body
so for example in influenza virus we induce a mucosal immune response so that sIgA produced and present in mucosal membrane

Question 18

why must we wait till 9+ months to vaccinate neonates

Answer 18

have maternal IgG (from placenta) and IgA (from breast milk) in their blood .’. mothers Ig will neutralise any antigen present - inc that of the vaccine .’. baby not able to develop immunity

Question 19

routes of vaccine inoculation

Answer 19

orally (polio)
intradermally (BCG)
subcutaneously (most vaccines)

Question 20

advantages of oral vaccines

Answer 20

avoid needles, mimics natural route of infection, ensures exposure to large immune surface, produces good sIgA

Question 21

what is a monotypic antigen

Answer 21

all strains of the antigen are similar .’. when exposed to it once become immune to all strains of the antigen

Question 22

what is a polytypic antigen

Answer 22

antigens change frequently and different strains have very different antigens.
.’. can be reinfected multiple times - as immune system is naive to the new antigens

Question 23

what are the three types of vaccine we can give

Answer 23

live, attenuated organism
Killed, whole organism
Sub-unit Vaccines

Question 24

how may we attenuate an organism

Answer 24

by serial passage (growing it in different environment .’.lower virulence)
recombinant genetics
select natural strains that are attenuated

Question 25

why do we give killed polio vaccine as opposed to attenuated

Answer 25

polio vaccine type 1 has 57 mutations. however type 2 and type 3 =few mutations.
so t2/3 can easily mutate back to virulent form when replicating. although patient may not show symptoms (due to cross-specie protection) they can shed the virulent polio virus and infect nonvaccinated individuals leading to a new outbreak

Question 26

issues with using killed, whole organism vaccines

Answer 26

dead organisms= poor cell mediated response (bc dont replicate), likely to cause reactgenicity (may act as allergen, cause toxicity or result in autoimmunity)

Question 27

how do we deal with the poor cell mediated response in killed, whole organism vaccines

Answer 27

booster injections required in order to get individual up to sufficient immunoprotection
adjuvant may also be used

Question 28

why do we not need boosters in live attenuated virus vaccines

Answer 28

provide natural boosting as the virus is constantly replicating and growing and presenting its antigen over a period of time.

Question 29

what is in sub-unit vaccines

Answer 29

contain just individual components of an organism that will drive a good immune response.
eg proteins, toxoids, peptides etc

Question 30

what is a toxoid

Answer 30

a toxin produced by bacteria that has been inactivated using formaldehyde.
is still antigenic so can be used in subunit vaccines

Question 31

what happens when we inject a toxoid into an individual

Answer 31

recognised by bcells .’. Ig produced -> inactivates toxin and opsonises it .’. preventing it from damaging body
hence if ever infected again, body already contains Ig against it