Lec 5 - Vaccines Flashcards
What disease was used to eradicate smallpox and how did this happnen?
cowpox antigens similar to smallpox. infection generated immune response that was effective against smallpox infection
What is the main function of vaccines?
stimulate an adaptive response so on infection, 2ndry response occurs
Describe the 2 aims of vaccines
- long lasting immunity
- preventing transmission w/in populations
Describe some factors that favour the global eradication of a disease
- cost effective eradication scheme; programme more likely to be followed
- lack of animal carriers; prevents reinvasion of pathogen from animals
- lack of host long-term carriers; prevents reinvasion of pathogen from carriers
- lack of serovars of pathogen; one vaccine is effective
- effective & cheap vaccine available; worldwide programme possible
Why does herd immunity matter?
chance of transmission of a disease onto an unvaccinated person is greatly reduced if 2/3 of community is vaccinated
Give examples of available vaccines
- japanese encephalitis
- tetanus
- rabies
- anthrax
Give some features of an effective vaccie
- practical considerations; cost per dosage is low, effective
- induces T cell response (especally important in viral infections)
- induces neutralising antibody
- safe; will not give rise to infection
- long lasting
Describe briefly the 3 main types of vaccine
- subunit - parts of the pathogen
- attenuated - most effective. live pathogen in which strain has been weakened so will not cause disease, low virulence
- killed - does not replicate
Give the 4 methods of obtaining an attenuated strain for a vaccine
- bacteria - serial passage in vitro (BCG vaccine for M. tuberculosis)
- virus - serial passage through cell culutre in vitro (polio)
- adapted to low temps (viruses)
- genetically altered (cholera - removal of the A subunit)
how are killed vaccines killed?
heat / chemical treatment
For the table below, describe both LIVING and NON LIVING in terms of the definitions here
Even though subunit vaccines are regarded as the most effective (safest & few side effects) what are some of the downsides related to them?
require adjuvant, multiple injections, shortwr lived
Give 3 examples of subunit vaccines
- toxoid - inactivated toxin eg Diptheria
- subcellular fractions eg polysaccharide coat
- recombinant proteins - eg Hep B outer surface structure expressed in yeast
What is a conjugate vaccine and state why it is useful?
conjugatevaccine may be a polysaccharide coat linked to carrier protein - stimulates both a B and T cell response
what is the peptide vaccine for HPV designed to stimulate ?
hint; killed vaccines do not stimulate these
cytotoxic T cells
What are recombinant expression vaccines?
eg vaccinia virus used to express a HepB antigen
What is a DNA vaccine?
DNA inserted into an expresion vector and transfected into muscle cell (Eg) . expression can then be from when DNA inserts into chromosome / episomal
What are some of the barriers against creating an effective vaccine?
- cost
- high mutation rates of viruses eg/large no. serotypes
- lack of adequate medical infrastructure
- personal/religous reasons
- fake news eg decline of B. pertussis vaccines (USA - 80s/90s) leading to rise in Whooping Cough incidence
