Vaccines Flashcards
What are the three types of vaccines used?
Whole-killed, toxoid and live attenuated.
Immunisation can be…
Passive immunisation
Active immunisation or Vaccination
Define passive immunisation
The administration of pre-formed immunity from one person/animal to another person.
What are the limitation of passive immunisation?
Only humoral (AB) mediated - not work if cell mediated.
What are the advantages of passive immunisation?
Gives immediate protection.
Effective in immunocompromised patients.
What are the disadvantages of passive immunisation?
Short-lived, possible transfer or pathogens - serum sickness:
Example of passive immunisation
Specific immunoglobulin (Ig)
- Human Tetanus Ig (HTIG) rapid protection of exposed individuals.
- Human Rabies Specific Ig - Used after exposure to rabies to give protection until vaccine becomes effective.
- Human Hepatitis B Ig (HBIG)
- Varicella Zoster Ig (VZIG)
Human Normal Immunoglobulin (HNIG) (Passive immunisation)
Prepared from pools of at least 1000 donors, contains ABs against measles, mumps, varicella, hep a etc…
Convalescing serum (SARS Co-V2)
Pooled from people recovering from COVID-19 but clinical trial result suggests no overall increased efficacy against virus using passive immunisation.
Active immunisation
Non-living vaccines (whole killed and toxoids)
Live attenuated vaccines
The whole microbe vaccine
Bacteria or viruses grown in vitro and inactivated (formaldehyde or B-propionolactone)
Non-living vaccines do not cause infection - AG induced response that protects against infection - by non-self AG recognition.
Can also be cell-free toxoids - inactivated toxins.
Problems and limitations of whole killed vaccine
Organism must be grown to high titre in vitro (some cannot be grown in labs).
Whole pathogen can cause excessive reactogenicity (ADR)
Immune response are not always close to the normal response to infection.
Requires two shots.
Examples of bacterial whole killed vaccines
Diphtheria - toxoid (treated with formaldehyde)
Tetanus - toxoid
Pertussis - killed whole bacteria. Now acellular pertusses in the UK.
DTP given as one.
Cholera - heat killed bacteria.
Examples of viral whole killed vaccines.
Polio
Influenza vaccine
Hep A
Rabies
SARS-Co-V2
All inactivated viruses.
Live attenuated vaccines
Organism replicate within the host and induce an immune response which is protective against the wild type but does not cause disease.
More real life and provides better protection.
Attenuations
Cultured in such way that is does not cause disease when inoculated into humans.
Pathogenicity lost
Antigenicity retained
What are the advantages of live attenuated vaccines?
Immune response more closely mimics real infection - not fixed, no shape change.
Better immune response - lower doses.
Route of administration may be favourable (oral).
Fewer doses may be required.
What are the problems and limitations with live attenuated vaccines?
Impossible to balance attenuation and immunogenicity.
Reversion to virulence.
Transmissibility.
May not be attenuated enough for immunocompromised people.