MI: Bacterial and Viral Vaccines Flashcards
What R0 is required for a disease to be halted?
R0 < 1
R0 = number of people infected by one infectious person
What is herd immunity?
Form of immunity that occurs when vaccination of a significant proportion of the population provides a measure of protection for individuals that are not immune
What is the herd immunity threshold?
Threshold = 1 - 1/R0
What are the main immunological targets of vaccines?
Lymphocytes and antibody production
Which other response is important for live-attenuated vaccines?
T cell response to destroy infected cells
What are the three main types of memory cell?
- Memory B cells
- Memory killer T cells
- Memory T helper cells
Outline the immune response process to pathogens, as well as how it differs in post-vaccination
Capture of antigen by APC (antigen presenting cell – macrophages, dendritic cells)
- Innate system responsible for detecting PAMPs (Pathogen Associated Molecular Patterns) and DAMPs (Damage Associated Molecular Patterns) and presenting them through Pattern Recognition Receptors(PRR) to APC.
APCs present antigens to naïve T cells specific for that antigen, which recognises it as foreign and is activated. (Normally in lymph nodes)
Activated B cells can undergo cell division some will develop in plasma cells and others memory B cells.
Antibodies:
Neutralisation of infectivity owing to binding of viral surface antigens
Destruction of infected cells – antibody dependent cellular cytotoxicity. Macrophages and NK cells carrying Fc receptors bind to the antibodies.
If attenuated virus vaccine, then T cell response important in destroying infected cells
Goal of vaccination is to produce memory cells to the vaccine antigen
Post Vaccination:
- Entry of pathogen activated memory T cells which encourage immune response
- Memory B cells become active plasma cells (more antibodies produced at a faster rate)
- Memory killer T cell response may be reactivated
What are protective antigens?
one that can stimulate an immune response and prevent/alleviate the clinically important consequences of infection.
What are adjuvants?
substances of various kinds that enhance immune response
What’s an inactivated vaccine?
Inactivated
- Whole organism is detroyed (using heat, radiation or antibiotics)
- NO risk of causing infection in the host
- Immune response may not be particularly strong or long-lasting
What’s a live attenuated vaccine
Live attenuated
- Live organisms are modified to be less virulent
- Risk of acquiring virulence
- Should be avoided in pregnant women and immunocompromised patients
- Eg. MMR and yellow fever
What’s a toxoid vaccine?
Toxoid
- Inactivated toxin components
- eg. Tetanus or Diptheria
What’s a subunit vaccine?
Subunit
- Protein components of the microorganisms or synthetic virus-like particles
- Lack genetic material and are unable to replicate
- eg. Hep B, HPV
What’s a conjugate vaccine?
Conjugate
- Poorly immunogenic antigens are paired with a protein that is highly immunogenic (adjuvant)
- Haemophilus influenzae type B
What’s a heterotypic vaccine?
Heterotypic
- Using pathogens that infect other animals but do NOT cause disease in humans
- e.g. BCG
