Fever and Rash; Vaccine Preventable Disease Flashcards
What types of Vaccines do we use
What do you need to ask the parents in terms of a vaccine-preventable disease history?
What is this? what are the signs and issues of this disease?
Measles! (highly infectious)
- 2-3days of fever, conjunctivis, coryza, Kopliks spots (in mucosa of cheek, hard to find)
- Characteristic rash day 3-7, widespread and diffuse, most unwell at time of rash
- Complications commone; 10% get secondary infection (ear, pneumonia, croup)
- 1/1000 encephalitis (15% die, 25-35% long term damage
- Rarely SSPE: 7-10 years later; degenerative fatal NS disease from persistent measles infection
When do we vaccinate for measles
At 15 months then a booster at 4 years, as 10% of people don’t seroconvert on the first dose. Therefore we need the second dose to ensure >95% of people are immune
Do we still get measles outbreaks?
Yes, although the last epidemic was 1991, we still yes small outbreaks, mainly in people who either
- are not vaccinated
- or only had one dose!
2013: Lots in Waikato and Auckland, spread quickly accross the country
What is this rash indicative of
Purpura rash, that is indicative of Meningitis.
Meningicoccal Spesis
Spinal Fluid shouldn’t have WBC in it.
87% polymorphs (neutrophils)
Low Glucose: As glucose is what’s required for bacteria to survive, low glucose indicated infection
Gram negative coccobaccili: Grew Haemophilis influenza
Seizures in the first 48hrs of hospitalisation
Day 3 Head CT: bilateral extra axial collections and meningeal enhancement consistent with meningitis; ‘empiema’
Follow up: long course of IV AB’s
What is Bacterial meningitis and what is it caused by?
Meningitis: inflammation of the meninges (membrane) surrounding the brain
Bacterial meningitis caused by:
- S. pneumoniae***
- N. meningitidis
- Haemophilis influenzaae type b now rarely seen due to vaccination
- Different pathogens occur at different ages: eg newborn babies; Grp B streptococcous, gram negatives*
- also Viral agents (herpes simplex and enterovirus) and Tuberculosis*
What is the main part that is targetted of the different pathogens from the meningitis vaccines
They all have a distinctive sugary capsule coating that is the immunogenic part of them.
Why are polysaccharide vaccines not very good?
Polysaccharides have weak immunogenicity so we (especially young children age <2yrs) produce very weak antibody responses to polysaccharide antigens
We have poor immunological memory to polysaccharide antigens
How have polysaccharide vaccines been revolutionised?
But the introduction of Conjugate vaccinations
- Taking the long polysaccharide sugar chains on the capsule of the bacteria, taking them off and conjugating them into something more immune stimulating.
- Conjugate sugar to a protein and the IS will remember that life-long!!
Describe Conjugate Vaccines!
- Polysaccharide attached to a carrier protein
- taken up by B cells
- Carrier protein digested and antigen presented to helper T cells
- Converts a T-cell-independent carbohydrate antigen into a T-cell-dependent antigen
- Good immunogenicity in those 2yrs of age
- Good production of memory cells
How has conjugate vaccination helped Haemophilus influenza and what is HI?
A serious disease almost eradicated by immunisation in the developed world
- Gram-neg rod
- Typed by capsule
- Tybe b most important and prior to vaccination caused 95% of H.flu serious disease
Hib Vaccine
- Induces antibody to PRP capsule, protect against invasive disease
- Initial HiB vaccines were unconjugated and poorly immunogenic
- Conjugate vaccines now available
- PRP polysachareide linked to immunogenic protein
- Effective in young infants
- Reduces or eliminates nasopharyngeal colonisation
- If vaccine uptake is >80% invasive disease is virtually eliminated in a population
- Protective efficacy of vaccine >98%
- Given at 6 weeks, 3 months, 5 months and 15 months
- Still a few cases and most of these have been incomplelety or unimmunised
Streptococcus pneumoniae is a causative agent of Meningitis. Describe it as a bacteria
- Colonises the nasopharynx 5-10%of adults, 20-40% children at any one time
- Gram + coccus with a polysaccharide external capsule
- has >90 serotypes of capsular sugar which makes it really hard to vaccinate for! Causes escape of phagocytosis
- Invasive disease common in children <5yrs especially <2yrs and adults >65yrs
- Bacteraemia, sinusitis
- otitis media, pneumonia
- worldwide responsibility for million deaths/yr for children <5yrs
What is Invasive Pneumoccal disease (IPD)
- When pneumococci are isolated from usually sterile sites; cerebrospinal fluid (meningitis), blood (bactereamia) or pleural space/lung tissue (pneumonia)
- In children
- major cause of mortality and morbity <2yrs
- most common bacterial cause of otitis media
- For all age age groups
- commonest cause of bacterial pneumonia
- meningococci and pneumococcimost common causes
For many years, we used the polysaccharide vaccine ($20), what is this and why is it shit?
- Contains capsular polysaccharide from each of the 23 most common infecting serotypes
- used in splenectomy, immunosuppresed, chronic illness
- poorly immunogenic, doesn’t cause a big response, BUT for people with a poor immune system
- elderly (>65yrs recommended not funded)
- NOT useful in those younger then 2yrs; because you don’t have the ability to respond!
so the conjugate vaccine is finding immunogenic protein carrier (toxoids) and conjugating them to polysaccharides; these became part of the vaccine scheme in 2008
Since introduction into NZ and other countries The S.pn conjugate vaccine has had….
- 97% efficacy against invasive (meningits and bactereamia) pneumococcal disease aused by the vaccine serotypes
- 10% reduction in clinical pneumonia needing hospital
- 30% reduction in xray confirmed pneumonia
- some reduction in otitis media
- less AB resistant serotypes
- Significant protection of those not recieving the vaccine (older children >5yrs and adults = herd immunity)
What is Neisseria meningitidis
- Like Hib and pneumococci; the polysaccharide capsule is an important virulence
- N. meningitidis is an exclusive human pathogen transmitted by droplets from colonised upper respiratory mucosal membranes
- 12 serotypes based on capsular polysaccharode
- 90%meningitis cases are caused by strains belonging to serotypes A, B, C: these can cause epidemics
- serotype B happened early 2000’s stopped by vaccine, but there are still cases today!
What’s the prominent age group of meningitis patients?
Adolescent disease; mainly all <1yr, a smaller peak at 1-4yr
Why is the N. meningitidis so hard to make a proper vaccine against?
- Antibodies play a major role in protection
- Polysaccharide capsule poorly immunogenic compared with proteins of cell wall and outer membrane
- polysaccharide capsule of serogroup B composed of same sugars as those found on the surface of human immature neural cells
- so lymphocytes that could produce antibodie to capsule are deleted in fetal development (we may be immunotolerant to that particular poly sach.
- makes it really hard to make a vaccine against Type B!!!
What is the NZ MenzB vaccine
How effective is it as a vaccine!
(for meningitis type B)
- Outer membrane inside the capsule
- two outer membrane proteins (Por A and Por B) are the main components
- Antibodies to these proteins can cause
- Complement activation
- Phagocytosis
Didn’t produce lasting antibodies but helped lesser epidemic short term (so now no longer in use)
What meningicoccal vaccines are available?
Since type B is no longer in use
- Two purifed capsular polysaccharide and conjugate protein vaccines for serotypes
- A
- C
- W135
- Y
- Same principal as for HiB and pneumococcal conjugates
- Men. C conjugate vaccine on schedule fro aussie and UK
- New MenB (BexSero) vaccine on schedule in UK; uses 4 target proteins of serogroup B strain including the NZ MenzB porin targets
The majority of people are covered by vaccines, around 90-95% immunised, and have less of disparities in terms of ethnicity and socioeconomic status, so what are the issues still remaining and waht are some reasons for refusing immunisations?
- Timeliness:young infants not getting their vaccinations on time; which increases risk
- areas of challenge: maori and deprivation
- Challenges in maintaining:
- systems
- complex social media and anti-immunisation
- shifting priorites
- Theirs no link between MMR and autism, and has been disproven
MYTH: I heard excess vaccines give mercury poisoning
Thiomersal: a preservative in vaccines converted to ethylmercury in the body
- no vaccine now given on national immunisation schedue contain thiomersal; used in very small amounts as an adjuvant in adult DT and some flu vaccines (not the current one)
MYTH: Giving too many vaccines might weaken the immune system
THe number of antigens now used is less then the original small pox vacc.
What are the main anti-vaccine arguments?
