Vaccines

Question 1

Vaccine concept

Answer 1

We do not possess the IgG for new diseases hence by the time we do develop the appropriate antibodies, infection will have developed into disease

Vaccines help in exposing us to the pathogen antigens without progressing to disease by delivering a part of the organism that imitate the pathogen but isn’t pathogenic

Question 2

Types of vaccine

Answer 2

Live attenuated vaccines 
Inactivated 
Recombinant sub unit 
Toxoid
Conjugate polysaccharide-protein

Question 3

Live vaccines

Answer 3

Derived from disease causing microbes that have been weakened

Small dose is given that then multiplies in the host and stimulates an immune response

Response is virtually the same as a natural infection

Can cause pathophysiology and stability is an issue

Question 4

Inactivated

Answer 4

Microbes are inactivated by heat/chemicals (formalin) and therefore cannot replicate

Are not alive therefore cannot cause disease even in the immunodeficient

Requires 2-3 doses before immune effect occurs

Can be costly and prone to hypersensitivity

Question 5

Recombinant sub unit vaccines

Answer 5

Consists of one antigenic part produced by other programmed microbes

Response is usually Tcell independant- doesn’t need T-helper cells to stimulate B cells

Question 6

Toxoids

Answer 6

Chemically altered toxins that are no longer pathogenic

Hence antibodies produced during infection affect toxins rather than the organism itself

Highly efficacious and safe

Question 7

Conjugate polysaccharide vaccines

Answer 7

Prepared from extracted cellular fractions such as polysaccharides

Polysaccharides usually don’t illicit an immune response so are bound to a carrier protein, usually a toxoid

Usually targets childhood diseases

Question 8

Valency

Answer 8

Monovalent vaccines immunise against a single organism while multivalent vaccines immunise against several organisms or strains

eg. MMR - Measles, mumps and rubella

Question 9

Attenuating an organism

Answer 9

Pathogen passaged many times under stress conditions causing organism to replicate differently eg Slower replication, less virulence factors

Organism is then purified and formulated

Question 10

Recombinant sub unit vaccine process

Answer 10

Gene for sub unit is identified and inserted into host organism for production

The antigen is expressed in a safe and easy to grow organism

The antigenic sub unit is purified and formulated

Question 11

Conjugate polysaccharide vaccine production

Answer 11

Polysaccharide and carrier protein grown separately

Toxins removed from polysaccharide chemically

These are then covalently bonded, purified and formulated

Question 12

Haemophilus influenzae type B (Hib) vaccine

Answer 12

A polysaccharide conjugate

The Hib polysaccharide is conjugated with tetanus toxoid

Has to be given to kids 4x due to poor efficacy

Question 13

Adjuvants

Answer 13

Enhance protection from vaccines by promoting rapid, long lasting and broad immunity

They attempt to:

• induce immune response with less antigen available
• induce a broader response against strains not included in the vaccine
• overcome weakened immunity in the elderly etc

Question 14

How can adjuvants work?

Answer 14

Slows down antigen release thereby maintaining antibody levels

Stimulates DC maturation

Stimulates better utilisation of antigens

Induces CD4+(Th1)

Eg. Alum- Aluminium potassium sulfate AlK(SO4)2

Question 15

PCV (Pneumococcal conjugate vaccine)

Prevnar 13

Answer 15

13 different serotypes of pneumococcus separately conjugated to CRM197 carrier protein

The 13 conjugates are adsorbed onto alum and formulated