Vaccines Flashcards
Live-attenuated vaccine
Live-attenuated vaccines are made with a pathogen that is alive, but weakened. The pathogen can still reproduce a little bit, but not cause disease (e.g. the MMR vaccine)
Inactivated/killed vaccine
An inactivated or killed vaccine is what it sounds like. The pathogen is completely dead, but the antigen still promotes an immune response. The Salk polio vaccine is an example of this
Toxoid vaccine
Toxoid vaccines are used for some bacterial vaccines. Instead of including antigens from the pathogen’s surface, an inactivated version of a toxin that the bacteria produces is used. The DTaP vaccine is a toxoid vaccine.
Subunit vaccine
If only part of the pathogen is used to make the vaccine, this is referred to as a subunit vaccine (the Pertussis portion of the DTaP vaccine is a subunit vaccine).
Gene-based vaccine
Gene-based vaccines use the injection of a small amount of the pathogen’s genetic material rather than an antigen. The person’s cells uptake the genetic material and produce the antigen themselves, promoting an immune response.
Virus-like particles
Virus-like particles are a technology where the capsid or envelope of the virus is made in a laboratory, but without any genetic material inside. This way, the antigens can be presented to the immune system intact without any risk of the virus causing infection. The HPV vaccine uses this method.
Adjuvants (including what types are licensed in the US and how they might work)
Adjuvants are chemical additives to vaccines that are able to boost immune response through various mechanisms.
These include possibly clumping vaccine particles at the injection site (which recruits more APCs) or directly stimulating immune cells. In the United States, the only adjuvants that are licensed for use are aluminum-based compounds, which are included in the HepA and HepB vaccines, for example.
Thimerosol
Thimerosol is a preservative (not an adjuvant) containing trace amounts of mercury.
It was used in some vaccines to prolong shelf life. It has been taken out of all vaccines given to children under 6, and is only now included in some multi-does flu vaccine vials. It is often discussed as one of the possible reasons for the (disproven) hypothesis that vaccines are associated with autism. Some anti-vaccine literature suggests it was used in the MMR shot, however, it never was. Thimerosol was removed as a precaution and because other preservatives were used.
Epitope
An epitope is the specific chemical site on an antigen to which an antibody binds. It can be helpful to try to identify good epitopes for antibody binding in advance, instead of having to try many different antigens
Intramuscular injection
The most common method for delivering vaccines is intramuscular injection
Oral vaccines
Oral vaccines (like the Sabin polio vaccine) and nasal sprays are also used to deliver certain live vaccines
Cocooning
It is recommended that a booster be given to all caregivers for newborns and young children, as immunity fades over time. This process is called cocooning.
Be able to describe what each of the common vaccines fight against and what type of vaccine they are
Tdap/DTaP Vaccine
Covers Bordatella Pertussis infection (Whooping cough), diphtheria and tetanus
Made from inactivated toxin
Pregnant women (teens, adults) given Tdap vaccine regardless of whether previously vaccinated, DTaP for infants and young children (at 2,4,6,15 mo)
Recommended that a booster be given to all caregivers for newborns and young children, as immunity fades over time. This process is called cocooning.
MMRV Vaccine Measles, Mumps, Rubella (German measles), Varicella (chicken pox) Rubella in pregnant mothers can cause birth defects in children Attenuated virus made using tissue culture First dose given at 12-15 months, second at 4-6 years old MMR associated with slight increased risk of febrile seizures (about 1 more per 3-4,000 children than those not vaccinated) Pneumococcal Vaccine Pneumococcal disease caused by S. pneumonia Most commonly causes respiratory infections, including pneumonia Can cause meningitis (infects brain and spine), infect blood and inner ear Live attenuated vaccine Pneumococcal vaccine available, called PCV13 because protects against 13 different bacterial strains A more comprehensive vaccine, PCV23 protects against 23 strains and is recommended for young children (<2 yo and 65+ years old) Influenza Vaccine Must be made new each year due to new strains spilling over or circulating Strains determined by WHO sites in 5 different countries. CDC decides what strains will be included in the vaccine several months in advance Vaccine produced using chicken eggs in the past, though that is shifting more to human cell culture (using human cells grown in petri dishes in a lab) Most are killed virus, though the nasal spray is live attenuated
How reverse vaccinology/epitope prediction work
Reverse vaccinology is a method of epitope prediction.
An epitope is the specific chemical site on an antigen to which an antibody binds. It can be helpful to try to identify good epitopes for antibody binding in advance, instead of having to try many different antigens.
For certain diseases that mutate very quickly, it can be hard to identify epitopes that are consistent between strains. For example, there are many strains of HIV; far more than could all be separately included in one vaccine. If there is an epitope found on the surface of most or all strains of HIV, it could be used as a target for vaccine development.
In reverse vaccinology, researchers compare the genetic sequences of many different strains of the vaccine, looking for regions of the genome that are always consistent. These are areas that don’t mutate much, likely because the virus needs that very specific protein for survival. When they identify a region, it becomes a good antigen to potentially include in a vaccine.
How vaccine patches can be more effective than intramuscular injections
The newest form of delivery is called vaccine patches. They are still under development. The patches have microscopic needles on them coated in vaccine that penetrate just the very outermost layer of the skin when you put it on. You don’t feel the needles doing this. These patches hold a lot of promise for both preventing needle-sticks among health care workers and creating increased immunity.
You have far more immune cells right under the surface of your skin (to respond to scratches and cuts) than you do deep in your muscles. So delivering vaccine directly under the skin can increase the number of immune cells exposed, and thus the immune response.
