Bacterial and Viral Vaccines Flashcards
What is R0?
The number of people one sick person will infect on average.
What is the R0 of hepatitis?
2
What is the R0 of ebola?
2
What is the R0 of HIV?
4
What is the R0 of SARS?
4
What is the R0 of mumps?
10
What is the R0 of measles?
18
What is herd immunity?
Form of immunity that occurs when vaccination of a significant proportion of a population provides a measure of protection for individuals that are not immune.
Herd Immunity Threshold is the percentage of fully immune individuals required to stop the spread of disease.
HIT = 1 -1/R0
How do vaccines trigger the immune response?
Antigen Presenting Cells present part of the antigen on the cell surface.
APCs present antigens to naïve T cells (in lymph nodes) which are activated.
Activation of B cells in response to antigens (+/- APCs).
Proportion of activated B cells will mature into plasma cells.
Plasma cells produce antibodies specific for the vaccine antigen.
How do antibodies and T cells neutralise pathogen activity?
Antibodies bind to specific antigen:
- Neutralization of infectivity
- Antibody dependent cellular cytotoxicity
If attenuated virus vaccine, then T cell response important in destroying infected cells.
What is the goal of vaccination?
Goal of vaccination is to produce memory cells to the vaccine antigen.
Response to pathogen post vaccination is increased and more antibodies are produced.
Why are vaccines less effective in elderly people?
Decreased resevoir of naive T-cells.
What are inactivated vaccines?
Whole microorganism destroyed by heat, chemicals, radiation or antibiotics (e.g. Influenza, cholera, polio).
What are the advantages of inactivated vaccines?
Stable
Constituents clearly defined
Unable to cause the infection
What are the disadvantages of inactivated vaccines?
Need several doses
Local reactions common
Adjuvant needed
Shorter lasting immunity