MICRO: Vaccines Flashcards
Define variolation.
Deliberate infection with smallpox in the hope that a mild infection would follow and subsequent protection
Define R0.
The number of people that one sick person will infect on average / i.e. the basic reproductive rate
- Higher in a totally susceptible population
- If below 1 then transmission of disease is halted
Which of these viruses is most contagious?
HIV/ SARS.Measles/Hep C/Ebola
Measles
Define herd immunity. What is HIT?
- HI = a form of immunity that occurs when vaccination of a significant proportion of the population provides a measure of protection for individuals that are not immune
- HIT = Herd Immunity Threshold = percentage of fully immune individuals required to stop spread
HIT equation?
1 - 1/R0 = HIT
Which immune response is important in attenuated virus vaccines?
- If an attenuated virus vaccine is used, the T cell response is very important in destroying infected cells
- At the end of these processes, the main goal is to produce memory cells to the vaccine antigen
- Memory B cells
- Memory killer T cells
- Memory T helper cells
What are the benefits of antibodies?
- Antibodies (produced by plasma cells) lead to:
- Neutralisation of infectivity
- Antibody-dependent cellular cytotoxicity
Should live vaccines be avoided if…
1 and 2
But premature babies can also have a premature immune system.
Igs = may not produce immune response
High dose steroids = immunosuppressed
What are the advantages and disadvantages of inactivated vaccines? Give some examples.
-
Inactivated – e.g. Influenza, Polio (OPV = live attenuated; IPV = inactivated), Cholera
- Whole microorganism is destroyed by heat, chemicals, radiation or antibiotics –> no risk of causing infection
-
Advantages: :
- Stable
- Constituents clearly defined
- Unable to cause infection
-
Disadvantages
- Local reactions common
- Adjuvant needed
- Need several doses (shorter lasting immunity)
- Shorter lasting
What are some examples of live attenuated vaccines? What are the advatages/disadvantages?
-
Live Attenuated – e.g. MMR, yellow fever
- Live organisms are modified to be less virulent (there is, however, a risk of virulence)
- It is avoided in pregnant women and immunocompromised patients
A:
- Multiple antigens
- Long lasting immunity
- Sttrong immune response
D:
- Not for immunosuppressed
- Can directly cause the illness
- Potential for contamination
Give examples of toxoid vaccines.
- Toxoid Vaccines – e.g. Diphtheria, Tetanus
- Inactivated toxin components
What is an important consideration of subunit vaccines? Give some examples.
- Subunit – e.g. HBV, HPV
- Protein components of the microorganism or synthetic virus-like particles are used - MUST CHOOSE CORRECT COMPONENT
- They lack viral genetic material and are unable to replicate
Give examples of conjugate vaccines. Describe them.
- Conjugate – e.g. NHS bacteria vaccines, flu vaccines (?)
- Poorly immunogenic antigens are paired with a protein that is highly immunogenic (adjuvant)
What is an example of heterotypic vaccines?
- Heterotypic – e.g. BCG (bovine strain)
- Using pathogens that infect other animals but do NOT cause disease in humans or causes mild disease
Give an example of viral vectored vaccines.
Give examples of nucelic acid vaccines.
Directly encapsulated in lipid particles.
Quite unstable so can degrade in light/heat.
No DNA vaccines exist yet - worry about integration into human genome
Describe monovalent vs multivalent.
- Monovalent = targeting one strain
- Multivalent = targets several strains
What is the risk of components in vaccines?
Anaphylaxis
What are the determinants of primary vaccine immune response?
What are the detrminants of duration of vaccine response?
Learn main column
What are the common components of vaccines?
- Stabilisers are substances added to keep it chemically stable for transport from the site of production to the site of use
- Aluminium hydroxide is a commonly used adjuvant
- Preservatives are particularly important for multi-use vaccines where you don’t want the vials to be contaminated
- Antibiotics are used to prevent contamination
- Some trace components are left from the vaccine manufacture process
What are the contraindications/precautions for all vaccines/DTP/ influenza/ live vaccines?
What are some vaccination programme considerations?
- Vaccination should be administered before the peak-age-incidence of the disease
- Vaccination programmes either targeted towards high risk groups or widely disseminated to everyone
- Effective R0 needs to be <1
- Catch up campaigns to pick up anyone that missed vaccinations should be considered
What are the barriers to vaccination?
Access e.g. need good healthcare system, fridges etc
Anti-vaccination
What are the prerequisites for successful disease eradication?
- No animal reservoir
- Antigenically stable pathogen with only one/few strains
- No latent reservoir of infection and no integration of pathogen genetic material into the host genome (e.g. can’t eradicate HSV)
- Vaccine must induce a lasting immune response
- High coverage required for very contagious pathogens (e.g. measles)
