Immunisation Flashcards
- Recommended vaccine schedule for children in UK - Triple vaccine DTP - Vaccine against influenza - Poliovirus vaccines - MMR vaccine - BCG - Limitations of traditional methods of vaccine production - Future developments
3 types of vaccine
Live attenuated
Whole killed
Toxoids
Two types of immunisation
Passive
Active/Vaccination
Passive immunisation
Limitation
Advantages
Disadvantages
Pre-formed immunity from one organism to another
Requires antibody mediation
Immediate protection and effectiveness in immunocompromised hosts
Short-lasting
Possible transfer of pathogen
Serum sickness on transfer
Passive immunisation - types of immunoglobulin and examples and source
Specific
- human tetanus Ig
- Human Hep B Ig
- VZV Ig
Normal immunoglobulin - HNIG
Prepared from pools of at least 100 donors
Antibody against MMR etc
Active immunisation
Two types of vaccine
Vaccination
Live attenuated - weakened live strain of pathogen
Non-living - toxoid and whole killed
Live attenuated
Mechanism
Advantages
Problems
Limitations
Organisms injected replicate within host and encourage immune response
- B cells produce plasma and memory cells for future infection
- organism is living and shape preserved –> more realistic
- lower/fewer doses needed
- immune response mimics closely
- better route of administration
- Could result in disease
- balance immunogenicity and attenuation
- reversion to virulence
- transmission
- same effect in the immunocompromised?
Live attenuated examples
Bacterial
Viral
BCG - TB
Salmonella Typhi - given orally
Poliomyelitis - polio
Vaccinia - small pox
MMR
Some rely on herd immunity
Herd immunity
Social concept of immunity passed on within a community. A certain percentage (80%) are immunised against a disease therefore chance of spread is significantly reduced
Non-living vaccines
types
Toxoid
Whole killed
Rapid primary response - doesn’t cause disease
Memory immune response chart
Antibody conc (y) by weeks (x)
Flat latent period post 1st exposure
Steep rise during immunisation period - antibody titre increases and levels of IgG and IgM increase
Levels decrease as infection ceases.
2nd exposure - shorter latent period and faster response
Steep curve as antibody conc increases exponentially
Greater increase in IgG
Whole killed vaccines
mechanism
Problems and limitations
Examples
Bacterial and viral
Pathogens grown in vitro
Inactivated using toxic ages e.g formaldehyde
Protein or whole organism
Doesn’t cause infection
Antigens within induce immune response
- organism has to be grown in high quantity
- whole organism can cause excess reactogenicity
- immune response not always similar to real response
- need booster
- some bacteria expensive to grow
- adverse reactions
- Tetanus toxin
- DTP toxoid
- Pertussis acellular as part of DTP
- Cholera - heat killed to inactivate
- Polio vaccine
- Influenza
- Hep A
- Rabies
Cell free toxoids/inactivated toxins
No cytology
Purely antigens/toxin
Examples of pathogens without vaccine
Reasons for lack of vaccine
Malaria
HIV
Lyme disease
HSV
Mutation - shape change
Hard to grow
too many strains causing same disease
hard to obtain attenuated strains
New approaches
Recombinant proteins Synthetic peptides Live attenuated vectors DNA vaccines Polysaccharide-protein conjugates
Recombinant proteins
Production
Advantages and problems
Examples
Genetically engineered from pathogenic or mammalian cells
Do not have to be grown in vitro
Not all proteins generate strong enough response
Hep B surface antigen
Synthetic peptides
Production
Advantages
Problems
Machine made
Identifying epitopes is problem
Response may not be strong or broad enough
Live attenuated vectors
Mechanism - what do they do
Examples and problems
Who is at risk?
Express protein within an attenuated vector e.g vaccinia for small pox, BCG and adenovirus
- bacterial DNA in viral vector –> inserts DNA encoding protective antigen –> displays bacterial antigens –> antibody response encouraged
Immunocompromised people at risk
Vaccinia virus
Who is it given to
Smallpox
For immunocompromised
DNA vaccines
Mechanism
Form of transmission
Advantage
Express protein from pathogen in mammalian expression plasmid
Injection –> protein expressed
More effective when followed with live vector boost
Avoids need to grow DNA is cheap No live organism Poorer immunogenicity None on market
T independent antigen based vaccines
Who responds poorly and examples of vaccines given
Difficult to vaccinate against
Coated in polysaccharide capsule - cannot be processed and displayed on MHC class II proteins
–> no T cell help
Low magnitude antibody response
Low affinity
Mostly IgM
Little or no boosting on secondary exposure
Infants
- neisseria meningitidis
- streptococcus pneumoniae
- haemophilia influenzae
Mechanism of TI antigen –> protein conjugation
Examples
Will work if the B cells are specific B cells internalise antigen Expressed on surface Attracts SPECIFIC T CELLS Strong antibody response
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
Important changes to immunisation schedule
The addition of a pneumococcal conjugate vaccine (PCV) at 2, 4 and 13 months of age;
A dose of MenC vaccine at 3 and 4 months;
A booster dose of Hib and MenC vaccine (given as a combined Hib/MenC vaccine) at 12 months of age.
HPV vaccine for teenage girls
BCG no longer routinely given to teenagers. Targeted on at risk infants.
