Vaccination

Question 1

Explain the difference between active and passive immunisation

Answer 1

Types;

Active; Body makes its own antibodies, gives memory cells, protected against future infection

• Naturally acquired; Normal infection (chicken pox)
• Artificial; Vaccine

Passive: Antibodies given directly, short lasting immunity, no memory cell production

• Naturally acquired; mothers breast milk and across placenta
• Artificial; snake anti-venom

Question 2

Explain the meaning of the following types of vaccine, giving a specific example of each; live attenuated, inactivated, subunit, toxoid, conjugate

Answer 2

1. Live attenuated - MMR
   
   • there is the whole virus with reduced virulence
   • can give long term immunity but problems can arise
2. Inactivated - Hep A, Flu
   
   • dead form of the pathogen
   • long lasting but not lifelong immunity
3. Subunit – Hep B
   
   • Strong immunity to the antigens given in the vaccine
4. Toxoid - Tetanus
   
   • Injection of the toxin that causes the disease – no protection against the pathogen itself
5. Conjugate - Pneumococcus
   
   • The binding of a “weak” antigen to a “strong” antigen, so that the response to the “weak” antigen is bigger

•The Antigen

–Usually large and linear

–Not readily degraded

–Highly repetitive determinant

•The Immune Response

–Predominantly IgM

–Poor memory effect

–Low avidity antibody

Preparation of Conjugate Vaccines:

A.Random activation of high molecular weight or partly size reduced polysaccharide

B.Degradation of the polysaccharide to form active functional groups at both terminals

C.Degradation of the polysaccharide to form an active functional group at only one terminal​

Vaccine formulation;

1. Antigen; stimulate the immune response
2. Adjuvant; adjust and modulate the immune system, they potentiate the immune response (humoral, cellular or both)

• Delivery systems, usually a depot of antigen which is slowly released (mineral salts, surface, active agents, synthetic microparticles, oil-water emulsions, liposomes)
• Immune potentiators (Toxins and lipids, Nucleic acids (CpG), Peptidoglycan, Carbohydrates, Peptides, Cytokines and hormones)

3. Excipients; maintain pH and preserve

–Buffer, salts, saccharides, and proteins to maintain the pH, osmolarity and stability of the vaccine

–Preservative, e.g. phenoxyethanol, thiomersal etc.

Question 3

List examples of bacterial and viral infections for which vaccination can be a successful strategy

Answer 3

Properties of a good vaccine:

• Stimulates an effective immune response
• Is safe and does not cause adverse reactions
• Is inexpensive to manufacture and distribute
• Is stable
• Is easy to administer
• Should be simple for both manufacturer and regulatory authorities to control
  i. e. a good vaccine provides substantial benefit to health at low cost and low risk (quality control)

1. MenC vaccine
2. All-in-one paediatric vaccine
   
   • Whooping cough/tetanus/Diphtheria – Bordetella pertussis
   • Haemophilus influenzae type B – meningitis and septicemia
   • IPV – polio type 1, 2, and 3

Question 4

Medical microbiology: recall the basic principles of medical microbiology and it’s clinical relevance

Answer 4

1. Great use in identifying a bacterial/viral infection and then using this to assign the most appropriate treatment
2. Allows for quicker treatment, shorter stay, reduced cost, reduced morbidity and mortality
3. Prevents the development of more resistant strains of bacteria

• Diagnosis:

Sample acquisition -> Microscopy/culture -> identification