Vaccination Flashcards
Who invented the first vaccine? How?
Jenner observed milkmaids who contracted cow pox were immune to smallpox
- he attempted to deliberately induce immunity and in 1796, he successfully inoculated people with cowpox (Vaccinia virus) to protect them against smallpox (Variola virus)
What are the 6 controversies around vaccinations?
- MMR causes autism
- too many vaccines for infant immune systems to handle
- toxic chemicals used to preserve vaccines
- use of fetal cells for growing the virus used in vaccines
- too many vaccines for a baby to tolerate
- natural infection produces better immunity and makes the immune system stronger
Thimerosal
preservative for multi-dosage vaccine vials
- it is ethyl mercury and it is used at very low concentrations that are NOT toxic and does not accumulate in the body and leaves the body rapidly (methyl mercury is the one that accumulates)
used in hep and influenza vaccines
5 types of vaccines
- Attenuated whole-agent
- Inactivated whole-agent and subunit
- Toxoids
- conjugated
- nucleic acid
attenuated whole-agent vaccine
living but weakend microbes with the antigen intact but no virulence factor
- closely mimics the real infection and can get a CTL response (cytotoxic)
- 95% effective and life-long immunity because it stimulates both humoral (b-cell antibodies) and cell mediated immunity (t-cell) and memory cell creation
what are some diseases that have attenuated whole-agent vaccines?
Sabin (polio), MMRV (measles, mumps, rubella, varicella)
what are two disadvantages of attenuated whole agent vaccines?
- if the microbe in the vaccine mutates back to the virulent form, it may cause disease (if the microbe used in the vaccine reverts to its original form in the body)
- cannot use for people who have compromised immunity because theres still injection of antigen that their natural immunity cannot fight off
- also –> pregnant women should NEVER GET ATTENUATED WHOLE AGENT VACCINES
Inactivated and subunit vaccines
use whole microbes that have been killed by formalin or phenol or use parts of the organism like glycoproteins to inject into the person
what are some examples of inactivated and subunit vaccines?
- rabies, Salk (polio), one of the influenza vaccines, Gardasil (empty nucleocapsids), and HepB
what are some advantages of using inactivated and subunit vaccines?
- no replication in host; safe for immunocompromised people –> there are less antigens to stimulate the immune response and there will be no presentation of viral proteins on MHC 1 and no CD8+ cell mediated response
- no worry that vaccine will revert to wildtype
- pregnant women can be vaccinated using this so that they can be immunized against influenza
what is a disadvantage of inactivated subunit vaccines?
- immunity doesn’t last as long as attenuated vaccine and boosters must be given to ensure adequate exposure to the antigen, some memory cells can be made but it is only b-cell memory and not t-helper
toxoid vaccines
toxin of the pathogen is isolated and chemically treated to preserve the antigenicity but the toxin is non-functional
toxoid (the inactivated toxin) is then used as a vaccine to produce antibodies to the toxin, not the microbe
the antibodies to the toxin then bind to the toxin when it enters the blood stream and neutralize it, preventing it from binding to the intact cell and damaging it
what are examples of diseases that are given toxoid vaccines?
Diphtheria and tetanus
what is the downside of toxoid vaccines?
requires boosters for full immunity since no memory is produced
conjugated vaccines
- used for organisms that have polysaccharide capsules (poor antigens)
- children under 2 years cant respond to polysaccharides as antigens (only can respond to proteins)
so for them to get the vaccine, polysaccharides are combined with a protein which is highly immunogenic which fools the immune system to react to the protein and get immunity from the carbohydrate
what are some examples of conjugated vaccine diseases?
haemophilus influenza type b
neisseria meningitides
streptococcus pneumoniae
Nucleic acid vaccines
- DNA vaccines
- introduces a gene for an organism into human host cells, hopes that it will persist there and get transcribed
- induce cells to produce organism specific proteins that linger and keep the immune system activated to the organisms
- still in stage of Research and Development
- has alot of fall out
what is the Tuberculin Skin Test
test used to determine previous exposure to tuberculosis antigens (indicated by detection of memory cells)
- widely used to detect TB in NA because most people are immunized
How is the Tuberculin Skin test administered?
small amount of PPD (purified protein derivative) which are proteins from Mycobacterium tuberculosis are injected into the skin of the forearm.
a positive test is indicated by reddening and thickening of skin 48-72 hours after inoculation.
- this is caused by the infiltration of lymphocytes and macrophages after they have been mobilized by pre-existing memory cells
uses DELAYED CELL MEDIATED REACTION (TYPE 4) HYPERSENSITIVITY
downsides of tuberculin skin tests?
- cant be used in people are anergic (unresponsive ) like have a genetic deficiency or are immunocompromised/suppressed like AIDS patients as they do not react predictably to immune stimulus
- tuberculin skin test is not specific for M.tuberculosis - other mycobacteria species can also give a positive test
How do we indicate a positive Tuberculin skin test?
a positive test shows red and swollen circle at the site of the injection. the diameter of the swollen raised circle determines where exposure to TB has occurred) the size that is considered positive varies with the health status and age of individual.
QuantiFERON-TB Gold Test
- new blood test to detect TB exposure
- this test focuses on memory cells, and activated T-lymphocytes via production of interferon
- can be used to rule out or confirm a latent or active tuberculosis infection or previous BCG vaccination (TB vaccine)
- does not require patient to return in 48-72 hours to have results
How does the quantiFERON-TB Gold Test work?
- you take blood, separate t-lymphocytes and introduce Mycobacterium tuberculosis to the t-cells to see if they get activated
the activation is indicated by increased levels of interferon in the blood stream which is an indicator of exposure
downside of quantiFERON-TB Gold Test?
requires that a blood sample be collected from patient and processed in the lab within 12 hours of collection, this can complicate the clinical utility and availability of the test in certain situations
What is naturally acquired active immunity?
individual exposed to antigens in course of daily life where clinical or sub clinical infections can benefit immunity
i.e. unimmunized child get chicken pox and develops immunity after infection
what is naturally acquired passive immunity?
the natural transfer of antibodies
- maternal transfer of IgG antibodies over placenta
- IgA antibodies in mothers breast milk (protects baby from Haemophilus influenzas until 6 months of life by mothers IgG antibodies
What is artificially acquired active immunity?
result of vaccination, where specifically prepared antigens (vaccines) are introduced into the body
- these substances are altered so that they can no longer cause disease but can stimulate an immune response (i.e. immunity after mumps vaccine)
What is artificially acquired passive immunity?
- the introduction of antibodies from an animal or person who is already immune to the disease
i. e. varicella immunoglobulin given after exposure of unimmunized person to varicella
I.e. a child who has leukaemia given antiserum which has antibodies made from someone who already fought off the infection, and that is given to them to neutralize their infection
