Lecture 6: Vaccination Flashcards
what is vaccination/immunization?
Controlled exposure to a vaccine to produce immunity against the disease to prevent/reduce mortality and morbidity while promoting protective memory immune responses
Do we vaccinate for every disease?
No, only diseases that have high mortality/morbidity
what is the first misconception of vaccination?
Natural exposure is better. This is not true!
What is immunological memory?
The ability of the acquired immune system to respond more rapidly and effectively to pathogens that have been encountered before.
explain what this diagram shows and how vaccination is involved
When encountered by a primary infection, it takes round 7 days for the acquired immune system to get going. Sometimes, the infections work very quickly in these 7 days and bad things could happen to you, including death. If you survive these 7 days, the antibody and effector T cells will get rid of the infection and you start to get better. When you encounter a secondary infection, the T and B cells respond faster and the immune response is way bigger and better, so the infection should only be mild.
Vaccines intend to replace the primary infection so the memory cells are there for the next time you are exposed
What are the 2 types of memory cells?
T cells and B cells
What are the feature of B cells?
- make IgG rather than IgM (isotype switching)
- high affinity Ig (affinity maturation)
- high precursor frquency (clonal expansion)
- already express activation molecules
What are the feature of T cells?
- high precursor frequency
- already differentiated (Th1, Th2)
- already express activation molecules
- high affinity T cell receptor
what affect do memory T and B cells have on infection?
the infection does not occur, is sub-clinical or mild
Does only ‘living and eating healthily’ outweigh the need for vaccines?
No. this is another misconception.
what do we need for immunisation success?
- Safe and effective vaccines
- high uptake of completed immunisations
Are vaccines safe? what about the bad reactions to it?
- vaccines are safe
- more benefits than risks
- some vaccines have serious reactions, but these are rare and must be weighed against the protective benefits of vaccines.
does sanitation work better than vaccines?
No, it helps decrease disease but it not the only answer.
What are some practical considerations of a high uptake of vaccinations?
- cost: few cents to hundreds of dollars
- logistics: how, where, who (equity), stability?
- ease of administration: injection vs oral
the impact of these depends on a target group like health professionals or all children etc.
why are vaccines important even if the majority of people who get diseases are vaccinated?
This is another misunderstanding. Vaccines work at an individual and community (herd) level. If more people are vaccinated, then of course more people will be diseased as being vaccinated doesn’t mean you won’t get the disease. However, by having the majority of a population vaccinated, it allows for herd imminity to take place and protect people who are too young or too old to be vaccinated.
What is R0?
Basic reproduction number.
- how many people will you infect if you are infected.
explain the herd immunity threshold?
this is the percentage of people in a population that should be immune to the disease in a population (either through vaccination or having the disease before) in order to reduce the spread of the disease.
Which vaccines are given during pregnancy according to NZ immunisaiton schedule?
- Boostrix - Tdap
- Influvac Tetra - Influenza
Which vaccines are given at 6 weeks according to NZ immunisaiton schedule?
- Infanrix-hexa - DTaP - IPV - HepB/Hib
- Synflorix - PCV10
- Rotarix - RV1
Which vaccines are given at 3 months according to NZ immunisaiton schedule?
- Infanrix-hexa - DTaP - IPV - HepB/Hib
- Rotarix - RV1
Which vaccines are given at 5 months according to NZ immunisaiton schedule?
- Infanrix-hexa - DTap-IPV-HepB/Hib
- Synflorix - PCV10
Which vaccines are given at 12 months according to NZ immunisaiton schedule?
Synflorix - PCV10
Prorix - MMR
Which vaccines are given at 15 months according to NZ immunisaiton schedule?
- Priorix - MMR
- Hilberix - Hib
- Varilrix - VV
Which vaccines are given at 4 years according to NZ immunisaiton schedule?
- Infanrix-IPV - DTap-IPV
Which vaccines are given at 11 or 12 years according to NZ immunisaiton schedule?
- Boostrix - Tdap
- Gardasil 9 - HPV 9 (2 doses)
Which vaccines are given at 45 years according to NZ immunisaiton schedule?
- Boostrix - Tdap
Which vaccines are given at 65 years according to NZ immunisaiton schedule?
- Boostrix - Tdap
- Influvac Tetra - Influenza (annualy)
- Zostavax - HZV
How good is NZ’s vaccine uptake?
The goal is to have 95% full immunisation coverage by 2 years of age. However there are ethnic disparaties and a ‘for profit’ nature of the primary care system which has lead to NZ never reaching this target.
What happens if we fail to meet targets?
- diseases are not kept in control, which results in outbreaks.
How can we improve coverage?
- education
- active follow up
- equity in access to health care
- change in the healthcare model
what was the first vaccine?
edward jenner used cowpox to prevent small pox
(cow = vacca)
What are the 3 types of conventional vaccines?
- live attenuate vaccine
- inactivated vaccine
- toxoid vaccine
what are the feature of a live attenuated vaccine?
- clinical isolates or animal isolates
- attenuated/weakend by serial culture/passage or targeted mutation
what are some examples of live attenuated vaccines in NZ?
- MMR (measles, mumps, rubella)
- BCG (Tuberculosis)
- Polio (salk)
- rotavirus
- chickenpox and shingles (varicella)
what are the advantages of live attenuated vaccines?
- excellent immune response
- robust
- can be given orally
what are the disadvantages of live attenuated vaccines?
- can revert back to being fully virulent
- can result in disease in immunocompromised individuals
what are the features of killed vaccines?
- killed by heat, formalin inactivated
advantages of killed vaccines?
safe - they are dead so cannot cause disease
disadvantages of killed vaccines?
- variable efficacy
- require boosting
- reaction to formalin
- weaker/no cellular response because it is dead
example of killed vaccines in NZ?
- HepA
- polio (DTap-IPV-HepB/Hib Infanrix-hexa, GSK)
- Influenze - fluarix tetra (gsk)
- Influvac Tetra (Mylan NZ Ltd)
Features of toxoid vaccines?
- toxin is turned into a toxoid
- used where disease pathology is due to a powerful exotoxin or enterotoxin
- stimulates a protective Ig response
advantages of toxoid vaccine?
- excellent vaccines
- good efficacy
- safe
disadvantages of toxoid vaccine?
- impurities
- needs boosting
what are the types of modern vaccines?
- sub-unit vaccine
- vector vaccine
- DNA/RNA vaccine
features of sub-unit vaccines?
- part of the organism (proteins, peptides, vesicles etc)
- natural or recombinant, highly purified = safe
- can be purified from actual organism, expressed in bacterial, yeast, insect cells, mammalian cells or chemically synthesised.
- stimulates a specific immune response
- can be conjugated to carriers to increase immunogenicity
advantages of sub-unit vaccines?
- safe
- defined
- potential for transdermal delivery
disadvantages of subunit vaccines?
- cost
- efficacy variable (proteins and peptides are not immunogenic)
- no danger signals
- soluble
- small
so we will need strong adjuvants/excellent delivery system
is it possible to get sick from a vaccine?
no. they are not made from the whole organism so don’t contain all the genetic material and so you can’t get sick from it.
except from live attenuated vaccines as it involes the whole organism.
features of vector vaccines?
- DNA for vaccine antigen carried by a non/lowly pathogenic organisms (virus or bacteria)
- vectors must be attenuated or replication-deficient so will not cause disease.
- pre-COVID largely experimental
advantages of vector vaccines?
- stimulate excellent immune responses
disadvantages of vector vaccines?
- disease in immunocompromised individuals
- pre-existing immunity to vector organism
features of RNA vaccines?
- vaccine consists of RNA
- pre-Covid were experimental only
advantages of RNA vaccines?
- quick/easy to make
- polyvalent vaccine
disadvantages of RNA vaccines?
- stability
- little long term safety and efficacy data
