Vaccines Bacterial & Viral Flashcards
How is public health implemented in vaccine development?
Making and administering vaccines depends on quantitative data that tells us if it is emerging, how many people have it, and its course of spread.
With the two groups of meningococcal infections, this is an example where we don’t get cross-protection. This is because the polysaccharides of the two organisms are quite different. So, we need to develop a different vaccine for the specific organisms.
Describe how the MenB vaccine came about?
There was a vaccine that covered the groups C, A, W and Y. It was a conjugated (due the fact that infants are not very good at detecting polysaccharides) capsular polysaccharide vaccine.
In 2015, a Men B vaccine was developed, ad it was administered to all new born babies, then secondary shots given at 2 and 4 months, and a booster at 12 months.
There was a catch-up programme for babies born after 1st May 2015. However, other groups remained vulnerable (due to cost-effectiveness, shortage of supply, etc.).
What were some issues of the MenB vaccine?
- it was more reactogenic;
- not all serotypes of group B were covered (unlike MenC)
- there was some cross-protection against MenW
- it cost £75 per dose – needed to be £20 for cost effectiveness.
- it had 88% efficacy and strain coverage
- the duration of protection was 10 years
Describe the vaccine that was developed to protect against MenW.
There was the emergence of a new highly virulent invasive strain W. It had been increasing since 2009
It was decided to vaccinate risk groups:
- 14 – 18 year olds (school year 13)
- older university entrants (aged 19 - 25)
From spring 2016, it was decided that Men ACWY will replace Men C.
A catch-up programme currently offered to year 9 or 10 + catch –up year 11s.
What is the UK immunisation schedule for children/ young people?
Two months: DTaP/ PIV/ Hib/ HepB + PCV + rotavrisu + MenB
Three months: DTaP/ IPV/ Hib/ HepB + rotavirus
Four months: DTaP/ IPV/ Hib/ HepB + PCV + Men B
12 months: Hib/ Meningitis C + MenB
13 months: MMR + PCV
2-8 years: Flu (annual) nasal spray
40-60 months:DTaP/ IPV + MMR (second dose)
12-13 year old girls: HPV vaccine (2 doses, was 3)
13-18 years: Td/ IPV + MenACWY booster
Expand on the UK immunisation schedule for children/ young people and how it changed.
HepB was added because there were a lot of children acquiring it during birth from their HepB+ mothers, and it was a burden on the NHS, so a vaccine was introduced to prevent that.
PCV is given in boosting doses.
Rotavirus is a live attenuated viral vaccine. It was thought that you would only need to give attenuated live viral vaccines once, but it was found that they needed to be given twice. Turns out, although the vaccine works, it doesn’t protect children against severe forms of rotavirus.
MMR also needs to be given twice. This is because, ~10% of the people at the age of one year miss out, and because measles is such an infectious disease, there were still pockets of measles breaking out into the community. Thus, a second dose is needed.
Describe Haemophilus influenza type B.
It is a paediatric disease - usually affecting 6 month olds - 3 year olds (1/600 would acquire it).
Initially, it is a nasopharyngitis (often starting with viral infection).
It then spreads to an otitis media, sinusitis, bronchitis, pneumonia or sometimes epiglottitis (requiring a tracheotomy, croup.
It can develop into bacteraemia, septic arthritis, and meningitis (60% cases).
It can also develop into neurological disorders (33%) or death (5%) if not vigorously treated.
Describe the prevention of Hib meningitis.
The vaccine is very effective (99% of cases are Type B)
Type B - capsule polysaccharide vaccine linked to a conjugate: diphtheria/tetanus toxoids + outer membrane proteins.
Describe diphtheria.
It sits in the pharynx and undergoes non-invasive multiplication
The toxin is produced locally but acts at a distance:
- absorbed by lymphatics and has systemic effects, damages heart, kidney, nerves, adrenals
- kills epithelial cells and polymorphs
- has a gelatinous exudate
- ulcer - necrotic exudate - pseudomembrane
- local inflammation, swelling, lymph nodes - leading to Bull Neck
- respiratory obstruction
Describe tetanus.
It is caused by Clostridium tetani. These are gram positive rods, and are anaerobic.
Clostridium tetani lives in the soil; it is a spore-forming organism that can survive for years.
It can grow in a wound, and release toxins that have a systemic distribution and has an effect on the nerves.
This is what causes the paralytic excitation of nerves.
How does Clostridium tetani cause the paralysis?
The toxins block the release of the neurotransmitters (GABA) at the inhibitory synapse in the CNS.
This results in unopposed excitatory stimuli that gives you this spastic paralysis associated with tetanus.
The vaccine for this disease generated neutralising toxins; if you can neutralise them before they get to the synapses, they can not have their effect.
Describe whooping cough and its vaccine.
Whooping cough is also known as pertussis, and it combated by the DTaP vaccine.
It is a multi-toxin disease. It used to be a whole cell vaccine with just killed organisms, but it would give off a lot of toxicity.
Now we use a new low risk acellular vaccine (subunit). It contains outer membrane proteins, an adhesion molecule (adhesin) and the main toxin of the organism (pertussis toxoids).
This blocks the adhesion and neutralises the toxin, taking on an antibody role.
It is very effective.
What is the importance of administering the influenza vaccine?
This is mostly used to stop vulnerable people from getting the flu. It is also given to people surrounding them, so that they don’t become carriers and deliver the influenza to them.
What is the aim of the influenza programme?
- to protect those who are most at risk of serious illness (such as heart problems, etc.) or death should they develop influenza.
- to reduce the circulation of the virus.
Who is administered the influenza programme?
- all those aged 65 years or over
- all those aged 6 months or over in a clinical risk group
- those living in long-stay residential facilities
- those who care for elderly or disabled persons
- household contacts of immunocompromised individuals
- those working within health and social care settings
- those who work in close contact with poultry (as that is where new influenza strains are likely to come from)
- all children 2 – 9 years (most infections and transmission source)
