Lecture 6: Vaccines and Vaccinations Flashcards
How do vaccines work? general
Vaccines work by mimicking disease agents and stimulating the immune system to build up defenses against them.
What is the balance for vaccines
Vaccine efficacy and vaccine assosicated risk
Ability of a vaccine to work as intended to protect from illness to the probability of increased adverse event that harm the indiviuals or population
Weighing the risks and benefits of a vaccine : Areas of consideration
he incidence, severity, morbidity and mortality resulting from adverse vaccine reactions,
Case investigation to determine whether the vaccine presents a new suspected risk,
The probable mechanism and underlying cause of any vaccine reactions,
The preventability, predictability and reversibility of the risk of a vaccine reaction occurring,
The risks associated with alternative vaccines that protect against the same disease,
The risks associated with not vaccinating, i.e. the risks arising from the infectious disease in unvaccinated individuals.
Types of vaccines and example
- Live attenuated
TB
Measles
Yellow Fever
Rotvirus - Inactivated (killed antigen)
Whole cell whooping cough
Inactivated polio virus - Subunit
Acellular whooping cough
Hep B
4.Toxiod
Tetanus
Live Attenuated Vaccines (LAV):
Definiation
Immune response
LAVs are derived from disease-causing pathogens (viruses or bacteria) that have been weakened under laboratory conditions. They will grow in a vaccinated individual, but because they are weak, they will cause no disease or very mild disease.
Immune response
LAVs stimulate an excellent immune response, that is nearly as good as compared to an infection with the wild-type pathogen.
Live microorganisms provide continual antigenic stimulation giving sufficient time for memory cell production.
In the case of viruses or intracellular microorganisms where cell-mediated immunity is usually desired, attenuated pathogens are capable of replicating within host cells
Live Attenuated Vaccines (LAV):
Safety and Stability
Attenuated pathogens have the very rare potential to revert to a pathogenic form and cause disease in vaccinees or their contacts.
Immuno compromised are vunerbale as they can not clear the attenuated pathogen and therefore have the risk of causing the disease that is trying to be vaccinated against eg HIV
LAV:
Immune response vs safety and stability
Immune response:
Live micorbes provide continual antigenic stimulation, giving sufficent time for memory cell production
Attenuated pathogens are capable of replicating within the host
EXCELLENT immune response
Safety and Stability
Attenutated Pathogens can revert to orginal form and cause disease
potential harm to people with compromised immune system
Sustained infection
Contamination of tissue culture
immunisation cultures
not given in preg
less safe compared to inactivated
Inactivated (killed antigen) vaccines:
Def
Immune response
Definition
Inactivated vaccines are made from microorganisms (viruses, bacteria, other) that have been killed through physical or chemical processes. These killed organisms cannot cause disease.
Immune response
Inactivated whole-cell vaccines may not always induce an immune response and the response may not be long lived.
Several doses of inactivated whole-cell vaccines may be required to prime a sufficient immune response.
Inactivated (killed antigen) vaccines:
Safety and Stability
Safety and stability
Inactivated whole-cell vaccines have no risk of inducing the disease they are given against as they do not contain live components.
They are considered more stable than LAV vaccines.
Inactivated (killed antigen) vaccines:
Immune response vs safety and stability
IR:
May not give immune response in first dose
Repsonse may not be long lived (many doses)
LESS STRONG immune response than LAV
Safety:
No risk of inducing disease (no live components)
Safer than LAV
Subunit vaccines:
Def
Immune response
Definition
Subunit vaccines, do not contain live components of the pathogen. They differ from inactivated whole-cell vaccines, by containing only the antigenic parts of the pathogen. These parts are necessary to elicit a protective immune response.
Immune response
This precision comes at a cost, as antigenic properties of the various potential subunits of a pathogen must be examined in detail to determine which particular combinations will produce an effective immune response within the correct pathway.
Often a response can be elicited, but there is no guarantee that immunological memory will be formed in the correct manner.
Subunit Safety and stability
Like inactivated vaccines, subunit vaccines do not contain live components and are considered as very safe.
Subunit
Immune response vs safety
IR:
Must determine which combination of antigenic properties will make an effective immune response with the correct pathway
A response may be elicted but with no guarantee that memory will form for future repsonses
LESS STRONG THAN LAV
Safety:
Have no live components - no risk of infection
Safer than LAV
Toxiod vaccine Defination
Definition
Toxoid vaccines are based on the toxin produced by certain bacteria (e.g. tetanus or diphtheria). The toxin invades the bloodstream and is largely responsible for the symptoms of the disease.
The protein-based toxin is rendered harmless and used as the antigen in the vaccine to elicit immunity.
To increase the immune response, the toxoid is adsorbed to aluminium or calcium salts, which serve as adjuvants.
Toxoid vaccine safety and stability
Safety and stability
Toxoid vaccines are safe because they cannot cause the disease they prevent and there is no possibility of reversion to virulence.
The vaccine antigens are not actively multiplying and do not spread to unimmunised individuals.
They are stable, as they are less susceptible to changes in temperature, humidity and light.
