Immunisation Flashcards
What is immunisation?
- The process whereby a susceptible individual is rendered immune to an infection
- Immunity can be passive or active
- Aims of immunisation can range from eradication to preventing symptoms
What is passive immunisation?
- Transfer of pre-formed antibodies to a susceptible individual giving temporary protection from infection
- Occurs naturally - mother to baby via the placenta and breast milk
- Normal immunoglobulin
- Specific immunoglobulin
- Monoclonal antibodies
What is active immunisation-1?
-Live attenuated - traditionally generated by serial passage in tissue culture
-Pros = Replicate in recipient = excellent immune response
= More closely resemble natural infection= mucosal immunity as appropriate
-Cons = potential for reversion
=Potential for sustained vaccine strain infection
=Not suitable for all
What is active immunisation-2?
-Inactivated whole cell - Pathogen killed by chemical or physical processes
What is active immunisation-3?
-Inactivated toxin (toxoid) - Toxins chemically treated to eliminate toxicity whilst maintaining immunogenicity
What is active immunisation-4?
- Subunit recombinant proteins - Specific viral protein produced in a heterologous expression system
- Subunit - chemically purified - certain components of a pathogen are purified for use in a vaccine
What is active immunisation-5?
-Polysaccharides - purified bacterial polysaccharide
What is active immunisation-6?
-Conjugated polysaccharides - purified bacterial polysaccahride linked to a protein
What are Adjuvants?
- Agents that stimulate the immune system
- Aluminium phosphate and hydroxide are commonly used
- Thought to sequester antigen and cause inflammation
- More recently monophosphoryl lipid A, an oil-in-water emulsion of squalene and cytosine phosphoguanine have been used
- Development of new adjuvants may allow modulation of the type of immune response developed
Uses of vaccines - pre-exposure
-Children - According to the UK routine childhood immunisation programme
-Adults - 65 yrs of age- pneumococcal polysaccharide vaccine
= 65 yrs of age- annual influenza vaccine
= 70 yrs of age- varicella zoster (shingles vaccine)
-Pregnant women- influenza vaccine in any trimester prior to start of ‘flu season
= pertussis vaccine from 16 weeks gestation
-Adults and children at high risk due to underlying health conditions
-Those at risk due to occupation, lifestyle or contacts
Use of vaccines - post-exposure
-Immunoglobulins and some vaccines can be given after an exposure to reduce the chance of an individual developing a disease, or reducing disease severity should disease occur
-Examples:
=Wounds at high risk of tetanus- specific immunoglobulin
=Potential rabies exposure- course of vaccine +/- specific immunoglobulin
-Unvaccinated contact with confirmed measles case- vaccine, if contraindicated- consider normal immunoglobulin
Adverse effects of vaccines
- Related to either the immunogen or other components of the vaccine
- Most commonly local reactions- pain, swelling and redness
- General systemic effects- fever, headache and malaise
- Some vaccines may be associated with a rash- e.g. MMR, VZV
- Anaphylaxis is rare
- Other rare adverse effects vary by vaccine,
Contraindications to vaccines
-Very few people are unable to receive vaccines
-Consider:
=history of anaphylaxis to previous vaccine/vaccine component
=immunosuppression
=pregnancy
-Immunisation may need to be deferred:
=acutely unwell
=other vaccines given recently
=immunoglobulin therapy
