Vaccines Flashcards
What is a vaccination?
- Something that stimulates the immune system, without causing serious harm or side effects
- Basically, it is some form of antigen administered to the patient
What is the aim of immunisation?
- to provoke immunological memory to protect individual against a particular disease if you later encounter it…
- Reducing the morbidity and mortality of the infectious disease targeted by the vaccine.
What feature of the immune system is critical for the function of vaccines?
Immune memory
What type of immunity does vaccination provide?
Artificially acquired active immunity
- Artificially- you haven’t encountered the antigen naturally in its wild form
- Active- you are generating your own antibodies and own immune response against that antigen.
What is an ideal vaccine?
- Completely safe
- Easy to administer
- Single dose, needle-free
- Cheap
- Stable
- Active against all variants
- Life-long protection
How does vaccine work in the community?
Herd Immunity
Reducing Ro
What is Ro?
Definition: How many people an infected person goes on to infect i.e if Ro=1- each infected person gives one other person the disease.
If R0 < 1 the infection will die out in the long run.
If R0 > 1 the infection will be able to spread in a population.
The aim of immunisation is to reduce Ro less than 1!
What are the 3 potential fates of lymphocytes once activated?
- Clonal Expansion
- Formation of memory cells
- Affinity maturation ( B cells only)
Compare primary and secondary immune responses?
- Secondary response is faster and stronger
- Stronger just means that a higher quantity of antibody is released
How do vaccines stop infection?
- Boost immune response ( secondary response is faster and stronger)
- Kill infected cells (cytotoxic CD8+ T cells)
- Prevent pathogen entry into cells ( macrophage activation and antibody release)
What is found in a vaccine?
- Antigen (in various forms)
To stimulate the immune response to the target disease - Adjuvant (normally alum)
To enhance and modulate the immune response - Excipients
Buffer, salts, saccharides and proteins to maintain the pH, osmolarity and stability of the vaccine - Preservative, e.g. phenoxyethanol, thiomersal etc
- Water
In what forms can antigens be used as a vaccine?
- Inactivated Protein e.g. Tetanus toxoid
- Recombinant protein e.g. Hep B
- Live Attenuated Pathogen e.g. Polio/ BCG
- Dead Pathogen e.g. Split Flu vaccine
- Carbohydrate e.g. S. pneumoniae
What are inactivated protein vaccines and how do they work?
- Examples: tetanus and diphtheria toxoids
- What: Chemically inactivate the bacterial exotoxin
- How the vaccine works: Stimulates the production of a complementary antibody that will block the action of that exotoxin
What is BCR selection?
- B Cell antigen specificity is determined by the BCR (B cell receptor) which is surface bound antibody.
- BCR has a light and a heavy chain
- Each is encoded by an individual gene, which is made by recombination of building blocks
- This occurs in the bone marrow before the B cell is released
What is an example of a recombinant protein virus? What are the advantages and disadvantages?
- Example: Hep B Surface Antigen (HbSAg)
- Description: recombinant protein from pathogen
- Mechanism: Induces classic neutralising antibodies
- Advantages: Pure, safe, because low strain variation and human only host highly protective
- Disadvantages: Relatively expensive, has not proved to be answer to all pathogens (see below)
