Vaccines Flashcards
The 2 types of immunisation
Active and passive
What is passive immunisation?
The administration of pre-formed “immunity” from one person or animal to another person
Limitation of passive immunisation
Only humoral (antibody) mediated
Advantages of passive immunisation
Gives immediate protection, useful for immunocompromised patients
Disadvantages of passive immunisation
Short-lived, possible transfer of pathogens
Examples of passive immunisations
Human Tetanus Ig (HTIG)
Human Rabies Specific Ig
Human Hepatitis B Ig (HBIG)
Varicella Zoster Ig (VZIG)
Active Immunisations can be…
Non-living vaccines and live attenuated vaccines
What are the 3 main way to make a vaccine?
Using whole virus or bacterium
Parts that trigger the immune system,
Just genetic material
Problems with whole killed vaccines
Organisms need to be grown in lab, can be difficult and expensive
Can cause excessive immunological responses
Immune responses are not always close to normal response to infection
Usually need at least 2 shots
Examples of whole killed bacterial vaccines
Diptheria, tetanus, pertussis (whooping cough), cholera
Examples of whole killed virus vaccines
Polio, influenza, Hep A, Covid, Rabies
Attenuation
Where an organism is cultured in such a way that it does not cause disease when inoculated into humans. Loses pathogenicity but retains antigenicity (shape)
Advantages of live attenuated vaccines
Immune response more closely mimics the real infection,
Lower dose required
Fewer doses required
Can often be taken orally
Problems of live attenuated vaccines
Often impossible to balance attenuation and immunogenicity
Transmissibility
Examples of live attenuated bacterial vaccines
Bacille Calmette-Guerin (BCG for TB)
Salmonella typhi
Examples of live attenuated viral vaccines
Poliomyelitis
Vaccinia virus
Measles, Mumps and Rubella
What are some reasons that there aren’t vaccines for all pathogens?
Pathogen too difficult to grow,
Killed pathogen not protective (shape change)
Impossible to obtain attenuated and suitably immunogenic strain
Recombinant proteins
Genetically engineered and produced from bacteria, yeast, insect or mammalian cells
Major difficulty for recombinant proteins
Hard to find protein or proteins that are protective and generate a strong enough immune response
Synthetic peptides
Peptides synthesised directly using a machine - avoids the need for pathogen growth
Live attenuated vectors
Composed of a safe living attenuated viruses that have inserted genes encoding foreign antigens, which are displayed to the immune system.
Example of live attenuated viral vector
SARS-Co-V2
DNA vaccines
A mammalian plasmid containing DNA that encodes for the foreign protein of interest is injected directly
mRNA vaccines
mRNA of the target foreign protein is synthesised in vitro, complexed with lipid nanoparticles that stabilise and protect the mRNA from degradation, allowing hte mRNA to cross the plasma membrane.
mRNA translated and protein presented on surface with MHC, stimulates immune response
T-independent antigens
bacterial capsular polysaccharides cannot be processed and presented on MHC class II
When do kids take the PCV (pneumococcal conjugate vaccine)?
2 months, 4 months, 13 months
When do babies get doses of MenC vaccine?
3 and 4 months
Is BCG routinely given to teenagers?
No, not anymore, targeted for at-risk infants
