Vaccination and Immunisation Flashcards
Has smallpox been eradicated ?
Yes
Define the Pasteur principle.
- ISOLATE pathogen
- INACTIVATE
- INJECT
What are some of the vaccines we can expect in the coming years ?
Meningitis, Papilloma, Avian Flu
What are the essential features of vaccines ?
♠ Must provide effective protection without risk of causing disease or severe side effects
♠ Should stimulate correct arm of immune response, ie antibodies or effector T cells (i.e. should stimulate same response as the actual disease, most of the time stimulate neutralising antibodies to prevent re- infection)
♠ Protection should be long-lived
♠ Stable for long-term storage and transport
♠ Economically affordable for widespread use
Identify the main types of vaccines.
Live Attenuated Killed Extract Recombinant DNA
Describe the main features of live vaccines.
Organisms capable of normal infection and replication. Not used against pathogens that can cause severe disease.
Describe the main features of attenuated vaccines + give examples of attenuated vaccines.
Organism is live, but ability to replicate and cause disease reduced by chemical treatment or growth-adaptation in non-human cell lines (e.g. measles, mumps, rubella).
Describe the main features of killed vaccines + give examples of killed vaccines.
Organism killed by physical or chemical treatment. Incapable of infection or replication, but still able to provoke strong immune response (e.g. B.pertussis, typhoid)
Describe the main features of extract vaccines + give examples of extract vaccines.
Materials derived from disrupted or lysed organism (e.g. capsular polysaccharides). Used when risk of organism surviving inactivation steps (e.g. flu, pneumococcal, diptheria, tetanus).
Describe the main features of recombinants vaccines + give examples of recombinant vaccines.
Genetically engineered to alter critical genes. Often can infect and replicate but does not induce associated disease (e.g. HPV).
Describe the main features of DNA vaccines.
Naked DNA injected. Host cells pick up DNA and express pathogen proteins that stimulate immune response
What are the main risks associated with vaccines ?
Risk of allergic response: not a response to the vaccine itself, but to something with the vaccine (stabiliser, preservative). e.g. eggs
Which type of vaccine is the best ? Why ?
-In general the most effective vaccines
have been live or attenuated
-Living or attenuated organisms express proteins and stimulate the immune response in a manner which most closely resembles normal infection
What is the relationship between safety and effectiveness of vaccines ?
Paradoxically, the safer the vaccine, the
less effective some have been
Define herd immunity.
The resistance to invasion and spread of an infectious agent in a group or community, based on the resistance to infection of a high proportion of individual members of the group (resistance is a product of the number susceptible and the probability that susceptibles will come into contact with an infected person)
i.e. If enough are vaccinated then the chances of an unprotected person meeting a pathogen becomes small. The population remain essentially resistant.