Lecture 31: Immunisation

Question 1

What are the various methods that vaccines use to confer immunity? and what immune components they use.

Answer 1

• Protein antigens; T-cell dependent AB
• Polysaccharide antigens; T cell independent AB
• Live viral antigens; AB, CD8 cytotoxic cells
• mRNA vaccines; AB, CD8 cytotoxic cells

Question 2

How are vaccines classified?

Answer 2

• Live attenuated vaccines (bact. or virus)
• Inactive/subunit/conjugate vaccines
• Recombinant or experimental (genetically engineered vectors, DNA and RNA vaccines)

Question 3

What is meant by inactive/subunit/conjugate vaccines and what are some examples?

Answer 3

• Whole viruses or bacteria or fractions
• Protein based vaccines - toxoids (inactive bacterial toxin), subunit or component
• Polysaccharide-based vaccines (pure cell wall polysaccharide from bacteria)
• Conjugate Polysaccharide vaccines (cell wall polysaccharide chemically linked to a protein)

Question 4

What are some examples of live vaccines and potential issues?

Answer 4

Generally long term immunity; These pathogens replicate and produce immunity but (usually) not illness

• Viral; MMR, Varicella, Oral polio vaccine
• Bacterial; BCG, oral typhoid
• Reassorted; Rotavirus vaccine

Can cause problems in immunocompromised people

Question 5

How do inactivated vaccines work?

Answer 5

Killed antigens (pathogens) are used but dont develop long term immunity with one dose therefore repeat immunisation is necessary

Can also use fractional component vaccines

• i.e subunits (Hep B, influenza)
• i.e toxoids (Diptheria, tetanus)

Question 6

How do whole live organism vaccine compare to killed organism or components of organism when measuring antibody response?

Answer 6

Whole live organism will produce peak antibody response.

Killed/components requires multiple vaccines to establish similar level antibody response.

Question 7

What are some examples of recombinant vaccines: and what makes them recombinant?

Answer 7

Hepatitis B vaccines; Segment of hep B virus gene into yeast expression system

Live attenuated influenza vaccine; Engineered to replicate effectively in mucosa of nasopharynx but not in lungs

Question 8

How does the type of vaccine correspond to NZ immunisation schedule?

Answer 8

In the youngers months of life subunit or conjugate vaccines are given because the immune system is less developed and immune issues could not be established yet.

After 12 months, attenuated live vaccines are used (confident there are not immune issues)

Question 9

Describe two childhood vaccines that consist of multiple antigens:

Answer 9

DTaPIPVHepBHiB
- 6in1; Diptheria, tetanus, acellular pertussis, inactivated polio, Heamophilus influenzae type B, hepatitis B. All component antigen vaccines. Given at 6wks, 3mths, 5mths, 4 years.

MMR

• All live attenuated vaccines
• Given at 12 months and 15 months

Question 10

Write some notes on tetanus as a pathogen:

Answer 10

• Clostridium tetani; Anaerobic, spore forming (soil, in claws of animals that bury poop), gram positive baccillus
• Penicillin senstiive
• Toxin symptoms; 10 days post exposure of wound to dirt/soil = muscular rigidity caused by tetanospasmin toxin

Question 11

What are the clinical features of tetanus:

Answer 11

Arching of back, facial grimace ‘lock jaw’

• Most at risk 60+

Question 12

Write some notes on neonatal tetanus:

Answer 12

• Entry via umbilicus to infant of incompletely or unimmunised mother (developing world)
• Infant has no passive immunity (IgG passage)
• Failure of aseptic technique during birth

Question 13

Describe passive immunisation when it comes to tetanus:

Answer 13

Passive immunisation: Human or equine tetanus IgG

• Acquired immunity through transfer of serum Ig
• Neutralises unbound toxin
• Shortens the course, lessens disease severity, improves survival
• REQUIRED if dirty wound and no previous tetanus immunisations

Question 14

What are the advantages and disadvantages of passive immunisation?

Answer 14

Advantages: Immediate protection

Disadvantages:

• No long term protection
• Risk of transmission of other disease from donor
• Expensive and not always easily available
• Potential serum sickness from injection of another persons/animals serum

Question 15

Write some notes on bordetella pertussis as a microbe and how its spread:

Answer 15

• Whooping cough
• Gram negative bacilli
• Preventable COD
• Deposited in resp. tract by aerosol droplets produced by the cough, very infectious

Question 16

What is the clinical manifestation of pertussis?

Answer 16

• Catarrhal phase (1-2 weeks); runny nose, conjuctive infection, malaise
• Paroxysmal phase (1-10 weeks); Short expiratory burst of rapid cough then insp. gasp and high pitched whoop
• Convalescent phase (weeks-months)

Question 17

What are the complications of pertussis?

Answer 17

• Secondary bacterial infections i.e pneumonias

- Encephalopathy, seizures, apnoea

Question 18

What is the treatment for pertussis?

Answer 18

• Azithromycin
• May shorten illness if started early.
• Decrease infectivity but: do little in established illness

Question 19

What is the new pertussis vaccine?

Answer 19

Accelular vaccine

• Number of virulence factors
• Much higher efficacy

Question 20

What are the recommendations for pertussis vaccination?

Answer 20

• Parents and other adults living the households with young children, or working with them ie teachers, childcare, drs
• Family members are the source of infections in most cases b/c immunity wanes and they develop a reservoir of pertusis

Question 21

What is happening in polio?

Answer 21

Poliomyelitis

• Destroys LMN -> paralysis
• Predominantly in children under 5
• 5-10% die resp failure
• 0.5% have irreversible leg paralysis

Question 22

What are the types of polio vaccination?

Answer 22

• Live oral poliovirus vaccine (used in endemic countries)
• Intestinal immunity controls of wild virus circulation
• Rare, vaccine associated paralytic polio disease (1 per 2.4m)

OR

Inactivated polio vaccine

• 3 doses
• 99% effective

Question 23

A patient comes in with a hand laceration from their cat, it has been more than five years since their last tetanus shot. What do you do?

Answer 23

• Clean the wounds and stitch them up.
• Give booster tetanus shot
• If highly likely to contain tetanus then give passive vaccine i.e IgG