+380.000 other summaries
A unique study tool
A rehearsal system for this summary
Studycoaching with videos
Remember faster, study better. Scientifically proven.
Summary - Prevention 2 - Vaccination and prevention of infectous disease
2 Vaccination versus passive immunization
Vaccination is ‘ACTIVE’ immunization
Jenner injected infectious material. This is active immunization.
The body must compose its own immune response.
Effect: long-term immunity
Another possibility to get temporary protection is injection of
specific antibodies against a particular pathogen. This is a passive
mode of immunization. The body does not make an immune response.
The antibodies originate from persons or animals that had a prior
immune response against the infectious organism.
Effect: short-term immunity (dependent on antibody half-life)
When passive immunization?
- therapeutic/post-exposure (rapid effect required; ex. snake bite)
- prophylactic (to be prepared for an infection; ex. hepatitis A, tetanus)
3 Features of effective vaccines
- SAFE - V must not itself cause illness
- PROTECTIVE - must protect against illness resulting from exposure to live pathogen
- GIVES SUSTAINED PROTECTION - protection against illness must last for several years
- INDUCES NEUTRALIZING ANTIBODY - Some pathogens infect cells that can't be replaced. Neutralizing antibody is essential to prevent the infection of such cells.
- INDUCES PROTECTIVE T-CELLS - some pathogens, particularly intracellular, are more effectively dealt with by cell-mediated responses
- PRACTICAL CONCIDERATIONS - low cost per dose, biological stability, ease of administration, few side-effects
4 Live and Dead vaccines
Live and Dead vaccines
Live vaccines - live attenuated
For human non-virulent or attenuated/weakened microorganisms:
- Animal microorganisms (e.g. cow-pox)
- Human cultured and thereby changed microorganisms
- Killed, but intact microorganisms = COMPLETE MICROORGANISM
- Inactivated toxins of microorganisms (toxoid) = TOXOID VACCINES
- Antigenic structures of microorganisms = SUBUNIT VACCINES
Subunit vaccines may lack appropriate immunogenicity; they don't raise a full blown antibody response.
==> SOLUTION: CONJUGATED VACCINES
The subunit antigen is coupled to a carrier-peptide that induces a supporting T helper cell response.
Effective in younger children, longer immunity and memory responses, more effective protection;
Addition of adjuvants to a vaccine is essential for succesful vaccination.
Function of adjuvants?
- Bind and complex the antigen to increase antigen presentation (AL-hydroxide)
- Provide local storage (oil)
- Induce an inflammatory reaction (bacterial substances, cytokines)
6 Safety of vaccines
Potential problems of vaccines
7 Certain vaccines are not effective
- induced effector mechanism is inappropriate
- a too high risk for disease
- vaccination does not provide immunity due to antigenic variation of the microorganism
8 Research in vaccination of infectious disease
Improvement of antigen administration
- recombinant live vaccines: weakened viral and bacterial vectors for expression of vaccine genes --> enhances tissue-specific immunisation
- DNA vaccination: plasmid vectors for administration and expression of vaccine genes (or cDNA) through intramuscular injection
Improvement of adjuvants for adequate antigen uptake and priming of the immune response
Packaging of antigenic peptides in liposomes --> better uptake and loading in MHC 1
Current research in vaccination of infectious diseases aims at strategies for programming T-cell responses by triggering innate immunity.