12.3 Principles of vaccination Flashcards
Describe measles.
- Viral infection
- Extremely contagious
- Koplik’s spots in mouth and throat
- Rash
- Complications: meningitis, encephalitis, seizures, liver infection, optic neuritis, death
Describe haemophilus influenzae.
- Gram negative bacteria
- Causes a variety of illness (not the flu): pneumonia, meningitis, septicaemia
- Infants vaccinated
- Aka Hib
Describe poliomyelitis.
- Picornavirus
- Sepctrum of disease: asymptomatic, minor illness, non-paralytic, paralytic
- Eradicated in all countries except for Pakistan and Afghanistan
Describe the Varicella-zoster virus.
- Herpesviridae family
- Chickenpox
- Risk of shingles
- Postherpetic neauralgia
- Vaccine for over 70s
Describe tetanus.
- Sore forming, gram positive anaerobic bacteria
- Produces entotoxins which cause muscle spasms, jaw lock, pain, stiffness
Which antibodies are produced in the primary and secondary adaptive immune responses?
- IgM and then IgG
How do antibodies protect the host against infection?
- Binds to microbes, viruses and toxins
- Prevents them from reaching host cells
- Activate phagocytes (opsinisation)
- Activate (fix) complement
Aka neutralisation, opsonisation, complement activation.
What are the 4 types of adapative immunity?
Active
- Natural: getting infected naturally
- Artifical: getting a vaccine
Passive
- Natural: breasteeding, antibodies via placenta
- Artificial: directly delivering antibodies, no memory, short-lived
What are the advantages of passive natural immunity?
Aka breastfeeding and placental transfer of antibodies.
- Antibodies provide immunity to microbes currently / recently encountered by the mother in the local environment
- Provides cover to the neonate after birth whilst adaptive responses develop and before vaccination is effective
What are the features of effetive vaccines?
- Safe
- Protective
- Sustained protection (may require boosters)
- Induce neutralising antibody
- Induce protective T cells
- Practical considerations:
- Cost per dose
- Biological stability
- Ease of administration
- Few side effects
What immunogens can be used in vaccines?
- Live attentuated organism: strong response, risk of side effects (risk of causing disease, can revert to wildtype), used for BCG, measles, mumps, rubella
- Killed/inactivated organism: often less immunogenic, can still cause side effects
- Purified toxoids (inactivated toxin): e.g. Diptheria, Tetanus, Hep B, very successful
What is herd immunity?
If immunization levels are high (>90%) a disease can no longer circulate in a population
- Even unvaccinated individuals will be protected
- Can be used to totally eradicate a disease
- Will fail if: disease has an another reservoir (eg animals), or infecting agent undergoes antigenic shift (eg influenza changes)
What is the basic reproduction number?
Nuber of secondary cases generated by a typical infectious individual when the rest of the population is susceptible (ie. at the start of an outbreak).
R0
What is the critical vaccination level?
The proportion of the population that must be vaccinated to achieve the herd immunity threshold.
Vc
What is the vaccine effectiveness against transmission?
Reduction in the transmission of infection to and from vaccinated people compared with control people in the same population.
E
