Vaccines Flashcards
What causes small pox
Variola virus
What causes cowpox
Vaccinia Virus
This is a milder disease that can affect humans and induce cross immunity to smallpox
Innoculation with vaccinia
Disease that have been reduced because of vaccinations
Diphtheria Measles Mumps Pertussis Polio Rubella Tetanus Haemophilus influenza type b Hepatitis b
Passive immunization
The transfer of maternal IgG antibody to the fetus in utero or IgA to the child’s gut from breast milk
Active immunization
Vaccination with an antigen that elicits an immune response
Prior exposure to pathogen or related pathogen
The memory response (T cells, antibodies) protects from reinfection and/or disease
There are immunoglubulins available for post-exposure prophy
From human: -Hep A and B -measles -rabies -chickenpox, VZV -cytomegalovirus -tetanus From horse -tetanus -botulism -diphtheria Recombinant: Ebola
What can a vaccine do
Make the body think that it is infected
Elicits a memory of immune responses that is ready to go when a person is exposed to a pathogen
- blocks initial infection (sterilizing immunity)
- blocks spread in the body or establishment of chronic infection (HBV)
- lessen symptoms of infection
- shorten time of infection
- block the action of toxins (tetanus)
- reduce or eliminate the risk of virus-caused cancers (HBV, HPV)
- reduce opportunity of spread to other individuals by lowering the incidence in the population
Herd immunity
By vaccinating you are reducing the opportunity of spread to other individuals thus lowering the incidence in a population
Vaccines are usually not 100% effective - some people will not develop a protective immune response and not all people will receive a vaccine.
If enough people are successfully vaccinated, the chain of transmission can be broken and the incidence of infection will drop.
The viral reproductive ratio (r) is reduced to r<1
If there is no animal reservoir then a disease might be eradicated. Smallpox was eradicated as of 1979
Polio?
T/f measles outbreaks are entirely preventable
True
Vaccines must be used to be effective
Vaccine strategies
Inactivated
Attenuated
Subunit
Vector vaccines
DNA vaccines
Inactivated
Salk Polio vaccine, HAV, influenza shot.
Formalin (formaldehyde) is the most common inactivating agent.
Attenuated
Sabin Polio Vaccine, Measles, Mumps, Rubella (MMR) VZV, Yellow Fever, Influenza nasal spray (FluMist).
Subunit
HBV, HPV vaccines - make individual proteins from virus.
Vector
in development
Use a different, non-pathogenic virus to deliver genes for the one you are immunizing against.
Ebola - use an attenuated animal virus vesicular stomatitis virus (VSV) and insert the gene for the Ebola envelope protein.
People are then infected with the rVSV-EBOV vaccine, the virus replicates a little but does not cause disease.
A strong immune response is made as for an attenuated vaccine.
DNA vaccines
in development
Deliver a gene for a viral component directly using
DNA injected into the muscle.
The DNA is taken up by muscle cells that then make proteins for the antigenic component of the virus.
Polio vaccines
1955 Jonas Salk - Inactivated Polio Vaccine (IPV) Formalin used to inactivate virus
Requires 3 doses
1958 Albert Sabin - Live attenuated Oral Polio Vaccine (OPV) strong immunity against all 3 forms of virus
replicates well in gut but not in nervous system
became the vaccine of choice during the control of polio
can revert to disease causing form in rare cases (1/750,000)
After polio became contained and rare, in US there has been a switch back to IPV for safety reasons.
Herd immunity keeps the population safe.
There is now a push to eradicate polio from the world.
There are no animal reservoirs besides non-human primates.
Adjuvants
Agents like aluminum salts or oil emulsions like squalene that are added to non-live vaccine formulations
How do adjuvants enhance the immune response
- Hold the antigen in place, allowing a greater length of time for a response and aiding in presentation of antigens to macrophages.
- Stimulate localized inflammatory/innate immune response which recruits T and B cells to the site, thus enhancing the adaptive response.
How do adjuvants make is possible for less antigen to be used?
in each dose of vaccine, making a limited supply of flu vaccine, for example, be used in more people.
Adjuvants in flu vaccine are used in Europe but not the US.
Preservatives
Thimerosal (merthiollate)
Prevent growth of bacteria and fungi
They are added to vials with multiple doses of the vaccine
Thimerosal
compound containing ethylmercury it is cleared from the body more quickly than:
Methylmercury is the mercury compound that is in fish that we try to avoid it can build up in the body and be toxic.
Thimerosal was taken out of childhood vaccines in the United States in 2001.
Which vaccine never has thimerosal
Measles, mumps, and rubella (MMR) vaccines
Varicella (chickenpox), inactivated polio (IPV), and pneumococcal conjugate
Why are measles, whooping cough and polio returning?
NOT vaccinating
