Immunisation Flashcards
What is the main aim of immunisation?
To control communicable disease
How does immunisation work towards controlling communicable disease?
Prevent onset of disease (primary prevention)
Interrupt transmission
Limit or prevent consequences after course of infection (secondary prevention)
What are some ways that have been introduced to prevent the onset of disease?
Childhood immunisation, travel vaccines, routine vaccination for older people, occupational vaccines, high risk clinical groups
How do vaccines cause the immune system to become resistant to pathogens?
Teach immune system to recognise bacteria/viruses before the individual encounters them as potential pathogens, thus allowing the body to fight against them
What are the immunological mechanisms of immunity?
Active, passive and herd immunity
What are antigens?
Parts of bacteria/viruses which are recognised by the immune system = usually proteins or polysaccharides
How does the immune system respond to antigens?
Usually produces antibodies
What are antibodies?
Proteins which bind to antigens = very specific to individual antigens
What causes other immune cells to be alerted of an infection?
The forming of the antibody-antigen complex
How are B cells involved in the immune system?
Has role in humoral immune system, triggered to produce antibody when foreign antigen is encountered, mature in bone marrow
How are T cells involved in the immune system?
Have role in cell-mediated immune response,CD4+ and CD8+ cells, mature in thymus, orchestrate response by binding to other cells and sending out signals
What occurs in passive immunity?
Transfer of pre-formed antibodies (immunoglobulins)
What are some examples of passive immunity?
Mother to unborn baby = via placenta, lasts up to one year, not protective against everything
From another animal = human normal Ig, specific Ig
What are some of the antimicrobial substances that are involved in passive immunity?
Human Ig = hep B, rabies, varicella zoster
Anti-toxin = diphtheria, botulinum
What are the advantages of passive immunity?
Rapid action, useful post exposure and in outbreak control, can attenuate illness, can be used if contraindication to active vaccination
What are the disadvantages of passive immunity?
Short term production, short term window for use, blood derived, hypersensitivity reactions may occur, expensive
How do vaccines work?
Induce cell mediated immunity responses and serum antibodies
What are the types of vaccine?
Live virus vaccines and inactivated vaccines
What are some features of live virus vaccines?
Attenuated organism, replicates in host, used to mumps and measles etc
What are the different types of inactivated vaccines?
Suspensions of killed organisms (e.g whole cell typhoid) Subunit vaccines (toxoids or polysaccharides) Conjugate vaccines (polysaccharide attached to immunogenic proteins)
What are some contraindications to vaccines?
Confirmed anaphylaxis reaction to previous dose of same antigen/vaccine component, egg allergy (yellow fever, flu), severe latex allergy, acute or evolving illness (must wait until stable)
What are some contraindications to live vaccines?
Immunosuppression = primary, high dose steroids, HIV
pregnancy
What is herd immunity?
Protecting unvaccinated individuals through having sufficiently large proportion of population vaccinated = vaccinated people stop transmission
How is the proportion of the population that needs to be vaccinated in order to provide herd immunity calculated?
Derived mathematically based on transmissibility and infectiousness of organism, and the social mixing of the population
What is required for herd immunity to work?
There must be no other reservoir of infection
What are some features of the Scottish Immunisation Programme?
Single largest co-ordinated public health programme
Protection against 15 different diseases offered
>1.5 million people are offered
What is the purpose of a routine vaccination schedule?
To provide early protection against infections that are most dangerous to the very young and to ensure continued protection by providing subsequent vaccines
Why should vaccination schedules be followed as closely as possible?
The age at which the vaccine is given is based on age specific risk of disease, risk of complications and ability to respond to the vaccine
Should children still be given vaccines if they are older than what is recommended?
Yes = every effort should be made to ensure all children are vaccinated
What are the vaccines given in childhood?
Hexavalent, meningococcal group B, rotavirus, pneumococcal, Hib/meningococcal group C, measles/mumps/rubella, influenza (annually)
What makes up the hexavalent vaccine that is now given to children routinely?
Diphtheria, tetanus, pertussis, polio, haemophilus influenzae type B (Hib), hepatitis B
What are some vaccinations that may be given to children in at risk groups?
Flu (annually) = aged 2 or older
BCG = aged up to 16
PPV23 = aged 2 or older
Hepatitis B = all ages
What vaccines are included in adult programmes?
PPv23 = 65 year olds Shingles = 70 year olds Seasonal flu (annually) = aged 65 or older, pregnant Various selective programmes (travel, occupational)
Are doctors responsible for notifying health boards about certain diseases?
Yes = legal duty to notify health boards on clinical suspicion of specified diseases or health risk state posing significant public health risk
How should doctors get in touch to notify health boards of disease outbreaks?
Notify in writing within 3 days (includes emails)
Notify by phone as soon as possible if urgent (still also need to give notification in writing)
Do doctors need to wait for lab confirmation before notifying health boards of a disease outbreak?
No = diseases have to be notified as soon as there is clinical suspicion of their presence
What are some examples of diseases that health boards must be notified of?
Plague, SARDS, smallpox, cholera, HUS, diphtheria, necrotising fasciitis
What is diphtheria?
URTI characterised by sore throat and low grade fever
White adherent membrane on tonsils, pharynx and nasal cavity
What causes diphtheria?
Aerobic gram positive bacteria = Corynebacterium diphtheriae
What is meningococcal disease?
Invasive infection caused by Neisseria meningitidis = causes meningitis, septicaemia or both
What are some long term complications of meningococcal disease?
Neurological defects = hearing loss, speech disorders, loss of limbs, paralysis
What serotypes of meningococcal disease are there vaccines available for?
Serotypes A, C, W, Y135 and B
How is meningococcal disease spread?
Person to person contact through respiratory droplets of infected people = incubation period of 3-5 days
What questions do you need to ask when deciding if a vaccine should be offered?
Is it needed? = disease incidence/complications, case fatality ratios, age distribution, trends
Does it work?
What are some factors that may influence whether a vaccine is offered?
Cost, model of delivery, acceptability, political factors, aim of programme
What are the phases of new vaccine investigation?
1 = is it safe? is it immunogenic? 2 = how reactogenic is it? what dose should be used? how does it compare with current vaccines? 3 = is it efficacious? are there any safety issues? 4 = post marketing surveillance
What are the costs of vaccines?
Cost benefit and effectiveness important
Economic cost of disease = visits to GP, hospitalisations
Economic cost of vaccination = vaccine cost, adverse effects, opportunity costs
What does the acceptability of a vaccine relate to?
The safety issues associated with the vaccine
What is the decision to use a vaccine based on?
Considering the balance of benefits and risks = disease burden versus known risk of vaccine
When may a vaccine be removed or changed?
If the safety concerns are valid
What does the uptake of immunisations depend on?
Perception of relative risks and benefits
What are the benefits of vaccines for individuals?
Reduce burden of disease = acute infection, death, long term complications
Maintain underlying health
What are the benefits of vaccines at a population level?
Reduce community transmission = minimise spread
Reduce healthcare utilisation and societal burden
Tackle inequalities
What does elimination of a disease mean?
Reduction to zero of incidence in a defined geographical area
What does the eradication of a disease mean?
Permanent reduction to zero of worldwide incidence
What does it mean if a disease is said to be extinct?
The disease no longer exists in nature or in the lab
What is meant if a disease is said to be controlled?
It has been reduced to a locally acceptable level
