Lecture 27 - Immunisation Flashcards
How do vaccinations work?
- expose person to antigens, and then they will get an immune response and produce antibodies against this
- have memory antibodies so get a faster response when you get exposed again
Protein antigens - t cell dependent antibodies
Polysaccharide antigens - T cell independent antibodies
Live viral vaccines - antibodies, CD8 cytotoxic cells
Live attenuated vaccines
-the virus or bacteria is modified in the lab
-replicate and produce immunity but not illness
-generally lifelong immunity
-e.g viral - measles mumps, rubella, varicella ect.
e.g bacterial - tuberculosis, oral typhoid vaccine
re-assorted - rotavirus vaccine
however in immunocompromised people - may not be good
Inactivated vaccines
Most vaccines are these
• Whole viruses or bacteria, or fractions
• Protein-based vaccines
- toxoids (inactivated bacterial toxin), subunit or subvirion
• Polysaccharide-based vaccines
- pure cell-wall polysaccharide from bacteria
• Conjugate polysaccharide vaccines
- cell-wall polysaccharide chemically linked to a protein
- not lifelong immunity with one dose
- repeat immunisation necessary
whole viral - e.g polio
whole bacteria- cholera
now most are fractional vaccines e.g influenza
toxoids - e.g tetanus
Hep B vaccine
-recombinant vaccine
get a segment of hep B virus into yeast expression system
Childhood vaccines
6 vaccinations in one injection
- diphtheria, tetanus, acelular petussis, inactivated polio, haemophilus influenzae, type B, hepatitis B
- all are component antigen vaccines
-given at 6 week, 3 months, 5 months, 4 years
measels, mumps, rubella - all live virus vaccines, given at 15 months and 4 years
Tetanus
Caused by a bacteria that produces a toxin, and this toxin is quite nasty
Introduced at time of injury, especially deep penetrating dirty wounds
-symptoms generally occur around 10 days after exposure
-get get msucualr rigidity caused by tetanospasmin toxin
-is a problem in the undeveloped world - often can get entry at birth
Neonatal tetanus
- occurs quite often in developing world
- entry often from unimmunised mother
- infant has no passive immunity, no igG passed through mother
- failure of aseptic technique during birth
- there is a high mortality rate
- give all women of child-bearing age in high risk areas 3 doses of tetanus toxoid
Passive immunisation of tetanus
advantages
if someone has the disease or is at high risk of it
Passive immunisation - human or equine tetanus , antibodies are given to help person fight this
- this tetanus immunoglobulin is developed from other sources - e.g human serum
- this neutralises the unbound toxin
- this shortens the course, lessens the severity of disease, improves survival
- required if dirty wound and no previous tetanus immunisations
advantages - immediate protection
disadvantages - not long term protection, risk of transmission of other disease from donor , expensive and not alwasys available , can get side effects from having another persons or animals serum
need to have regular injections and then the top up!
Bordetella pertussis - whooping cough
- gram negative bacillis
- vaccine preventable
- highest mortality in first year of life
- highly contagious, household spread
- is spread by aerosol droplets and is very infectious
- catarrhal phase- 1 to 2 weeks - runny nose, conjunctival injection, malaise
- Paroxysmal phase - short expiratory burst of rapid coughs, then inspiratory gasp and high pitched whoop
- convalescent phase - weeks- months
Complications
-can get secondary bacterial infections such as pneumonia
Treatment - antibiotics are useful, erythromycin can shorten the corse of illness and also make you less infective later on
Pertussis vaccine
- whole cell vaccine (old vaccine)
- is made of killed whole cells virus particles
- however this had lots of local and systemic reactions
Now we use an acellular vaccine
- consists of a number of virulence factors
- very effective, however need 3 donese and then 2 booster doeses (hard to get people to come back and get booster doses)
however this immunity wears off, but can be susceptible as adults and can be carriers and can pass this on to unvaccinated infants
-so recommend - parents get this as well
Poliomyelitis
destroys lower motor neurons resulting in paralysis
- effects young children
- can lead to irreversible paralysis, and children can die from this
Polio vaccine
- used to be given as an orla vaccine, and gave good intestianal immunity
- then now have polio vaccine - incase someone from another country comes in with this
Healthy child - should you vaccinate
-need to talk about the side effects but also tell these so it still recommends the patient to get the injection
