defence and vaccination against bacteria

Question 1

what are the properties of a good virus?

Answer 1

a good vaccine provides substantial benefit at a low cost and low risk

Question 2

• state the endemic state :
• herd immunity :

what does R S q stand for?

Answer 2

R0 = basic reproductive number
average number of people one person will infect

S = proportion of population who are susceptible to disease

q = the herd immunity level

R = 1/S
S = 1 - q
q > 1- (1/R)

Question 3

what are the different phases of vaccine safety ?

Answer 3

• phase 1
  used for safety but also used to assess immunogenicity
• phase 2
  immune response but also expands safety
• phase 3
  protection studies
  placebo controlled double blind trials

Question 4

how to look at vaccine efficacy?

Answer 4

• the reduction in the incidence of disease amongst people who have received a vaccine compared to the incidence in unvaccinated people

it is determined by phase 3 testing

1- attack rate in vaccinated group / attack rate in unvaccinated group

percentage

Question 5

what is herd immunity?

Answer 5

Form of immunity that occurs when the vaccination of a significant portion of the population provides a measure of protection for individuals who have not yet developed immunity.

Question 6

formula for the herd effect?

Answer 6

1 - attack rate unvaccinated post introduction / attack rate unvaccinated pre introduction

Question 7

what three elements do vaccines consist of?

Answer 7

• antigen
  this stimulates the immune response
• adjuvant
  this enhances and modulates the immune response
• excipients
  Buffer, salts, saccharides and proteins to maintain the pH

Question 8

what are the UK immunisation programmes?

Answer 8

• pre primary school - MMR
  grils 12-13 - HPV
  secondary education - DT IPV

Question 9

what are conjugate vaccines?

Answer 9

Carbohydrate chemically linked to immunogenic protein.

• T cell recognition of protein carriers enhances B cell activation
• Promotes efficient antibody response to polysaccharide capsule

Question 10

what is a live attenuated vaccine?

Answer 10

A vaccine prepared from live microorganisms or functional viruses whose disease- producing ability has been weakened but whose immunogenic properties have not.

Question 11

who does the BCG work for?

Answer 11

gives some protection against TB in children but is ineffective against adult
pulmonary disease

Question 12

how do pathogenic bacteria evolve strategies to avoid host defences

Answer 12

• resist complement
  have thick cell wall
  capsule
• resist antibodies
  antibody protease
  antigenic variation
• resist phagocytosis
  polysaccharide capsule
  debilitate phagocytes
  hide inside other cells
• Inhibit Intracellular Killing
  Escape from phagosome
  block phagosome maturation