Immunisation Flashcards
Benefits of vaccination
Individual and population effect
I = immunity to infection P = Reduced transmission of infection + reduced disease in vaccinated and unvaccinated people = herd immunity
What are the types on antigens that we generally make antibodies against?
Protein antigens - T cell dependant antibodies
Polysaccharide antigens - T cell independant antibodies
Live viral vaccines
- antibodies, CD8 cytotoxic cells
Live viral vaccines
Live viruses or live bacteria
Not pathogenic, won in culture under various conditions to change their pathogenicity whilst retaining their antigenicity
“attenuated” vaccines
Inactivated vaccines
from early in the 20th century
Whole viruses, bacteria or fractions
Chemically inactivated
Now days is much better to look for key antigens / epitopes on an organism and present them to the immune system
Protein based vaccines: toxoids (inactivated bacterial toxin), subunit or subversion
Polysaccharide based vaccines doesn’t produce good immunity, so they’re often chemically conjugated to an immunogenic protein which serves as a carrier and stimulates a much better longer lasting immunity against a polysaccharide
Live vaccines
Modify virus or bacteria in a lab
Replicate and produce immunity but not illness
Generally lifelong immunity
They actually generate an immune response??
e.g. VIRAL measles mumps, rubella, varicella, oral polio vaccine
BACTERIAL: BCG (tuberculosis), oral typhoid vaccine
REASSORTED: rotavirus vaccine (Rotateq) (they’ve engineered specific genes into the capsid of a rotavirus, so theres a lot of different epitopes that are being responded to)
Can cause problems in immunocompromised people
Inactivated vaccines have been? is this good or bad for long term immunity?
Not lifelong immunity with one dose, because they can’t replicate so need to gives heaps of doses to produce enough antibody and sufficient B cell memory (repeat immunisation nessecary)
Examples of whole viral vaccines
Influenza, injected polio, rabies and hep A
Examples of whole bacterial vaccines
Pertussis, typhoid, cholera
Examples of fractional vaccines
subunits (hep B, influenza, acellular pertussis)
Toxoids, which have been purified to retain antigenic shape but lose their toxicity (diphtheria, tetanus)
The difference in dosing between whole live organisms vaccine dose VS killed or components of organism vaccine dose
Need to give more doses (at least 3) with the latter type because they lack the capacity to replicate and so therefore cant imitate as strong an immune response on the same injection amount
Hepatitis B recombinant vaccine: explain
segment of HBV gene into yeast expression system
Vaccines given earlier in life are different in what way?
Manly antigenic fragments, don’t need a super well developed immune system to be received, whereas the ones which imitate a lifelong immunity need to be given when you’re older and have a stronger immunity, also by this time you would know if the child had some sort of immunodeficiency
What is the Infeanrix-hexa vaccine?
6 vaccines in one injection: diphtheria, tetanus, acellular pertussis, inactivated polio, haemophilia influenzae type B, hepatitis B
All are component antigen vaccines
Given at 6wks, 3 and 5 months and 4 years
When is the MMR vaccine given?
Later than the 6 vax one because they’re all live viruses and you need to be sure patients immune system is sound
15months, 4 years
Tetanus
Clostridium tetani: anaerobic, spore-forming, gram postive bacillus, penicillin sensitive
Spores everywhere particularly manure/ soil
Easily induced at time of injury, especially deep penetrating dirty wounds
Toxin symptoms:
- about 10 days after exposure of a wound to dirt or soil
Clinical features: arching of back (opisthotonus) facial grimace (rises sardonicus) ‘lock jaw’
What type of vaccine is used for tetanus?
Toxin one, the effect is caused by toxins released from the bacteria
Demographics at high risk of tetanus?
In developed countries and those over the age of 60, whose immunity had waned
Neonatal tetanus
Accounts for 50% of tetanus deaths in developing world
Entry via umbilicus to infant of incompletely or unimmunised mother
Infant has no “passive immunity” - no IgG passed through from mother
Failure of aseptic technique during birth
Mortality rate > 90%
WHO plan for neonatal tetanus
aim is to eliminate
Give all women of childbearing age in high risk areas 3 doses of tetanus toxoid
How can you protect unborn babies who’s mothers have been exposed to tetanus toxin?
Passive immunisation
- Human or equine tetanus immunoglobulin (TIG) to protect the babe by acquired immunity by transfer of serum (Ig) from a donor to a non-immune person, this neutralises unbound toxin, shortens the course, lessens the severity of disease improves survival.
Required if dirty wounds and no previous tetanus immunisation
Advantages and disadvantages of passive immunisation
+ immediate protection
- not long term protection
- risk of transmission of other disease from donor
- Expensive and not always easily available
- Serum sickness (side effects) from injection of another persons or animals serum
Bordetella pertussis =?
as a cause of death
whooping cough
among 10 most common causes of death from an infectious disease; a leading cause of vaccine preventable deaths
90% in LEDC’s
Highest mortality in first year of life
How is pertussis transmitted?
Deposited in respiratory tract by aerosol droplets produced by the cough - very infectious
Pertussis: clinical manifestations
Catarrhal phase (1-2 weeks)
- runny nose, conjunctival infection, malaise
Paroxysmal phase (1-10 weeks)
- Short expiratory burst of rapid coughs, then inspiratory gasp and high pitched whoop (uncommon in infants and adults)
Convalescent phase (weeks to months)
Pertussis complications
secondary bacterial infections e.g. pneumonia
Encephalopathy , seizures, apnoea
Pertussis: treatment
Antibiotics
- Erythromycin (macrolide antibiotic)
May shorten illness if started early (during first few weeks of illness)
Decrease infectivity but: do little in established illness
Pertussis vaccine
acellular vaccine
contains a number of virulence factors and antigens
efficacy aprox 85%
3 dose schedule and 2 booster doses
High risk demographic for pertussis in NZ
about 1 death per year
Infants at highest risk of complications and death if no maternal antibodies via placenta or breast feeding
Importance of booster doses in pertussis protection
results in a pool of susceptible adults who never got the booster and who’s immunity has waned over time
Recommended for pertussis vaccine?
Parents and other adults living in households with young children, so that the parents don’t become a sink for the disease
also adults who are working with children
healthcare workers, particularly those working with newborns
Poliomyelitis from poliovirus
- what happens?
- predominantly affects
- destroys LMN’s resulting in paralysis, 1 in 200 irreversible (legs usually), 5-10% die from respiratory difficulty
- children under 5
The latest polio vaccine
Live oral poliovirus vaccine
Used where polio endemic
Intestinal immunity controls of wild virus circulation
Rare, vaccine-associated paralytic polio disease VAPP (1 case for every 2.4 million doses)
Inactivated polio vaccine
99% effective with 3 dose course
Most countries have changed from using OPV to IPV, because it doesn’t have the small side effect potential
