L31 Immunisation

Question 1

What type of immune cell response does
- Protein
- Polysaccharide 
-Live viral vaccines
-mRNA vaccines 
produce

Answer 1

Protein antigens (viral): require helper T cells to induce B cells to make antibodies

Polysaccharide antigens- (bacteria): b cells don’t need as much helper T cell involvement to get a response

Live viral vaccines
- generate B cell memory antibodies and exposure of viral antigens gets CD8 cytotoxic cells to get memory

mRNA vaccine codes for viral protein that is made by normal cells. = similar to live viral response.

Question 2

What are the 5 types of Vaccines, and give a good example

Answer 2

1. Live attenuated vaccines: modified/reassorted virus, bacteria
   - Eg. MMR, varicella vaccine.

2.a) Inactivated: killed viruses usually older vaccines: eg. rabies

Preferred:
b) sub unit: most immunogenic protein eg. acellular pertussis

c) conjugate vaccines: protein, toxoid, polysaccharide. eg. diphtheria toxoid

3. Recombinant/experimental: segment of DNA/RNA code for antigen into an innocuous vector
   eg. Hep B vaccine. Live attenuated influenza vaccine.

Question 3

Compare the antibody response of whole live organism vax vs killed organism/components of organism vax.

when are they given on the national schedule and why

Answer 3

Whole live organism/ recombinant: goes through full infectious cycle so generates long term immunity- wks-> yrs

Killed organism/components of organism requires repeat doses/boosters to get long term immunity as doesn’t cause an infectious cycle.

However safe to be given earlier 6wks -5mo, than whole live vaccines (12-15mo) as live ones can cause problems in immunosuppressed bbies.

due to transient immunity from mother, difficult to tell if immunosuppressed from 6wks, and mothers antibodies can also neutralise vaccine before bb has chance to generate their own antibodies anyway

Question 4

What pathogen causes tetanus, who is at risk of infection, presentation

Answer 4

Cloristridium tetani: anaerobic, spore forming gram + bacillus, penicillin sensitive

• Increased risk with deep penetrating dirty wounds (spores everywhere - mostly in manure/soil)
• Increased risk 60yr+ due to waning immunity
• Neonates in developing country: Failure of aseptic technique during birth due to unimmunised mother.

Presents:
10 days after exposure of wound to dirt: muscular rigidity caused by tetanospasmin toxin : arching of back. Facial grimace (lock jaw)

Question 5

What is passive immunisation: pros, cons and when is it used in tetanus treatment

Answer 5

Transfer of serum Ig from human/equine donor to a non immune person. Neutralises unbound toxin shortening the course,severity of disease.

Required if dirty wound + no previous tetanus immunisations as direct immunisation is too slow

Cons: no long term protection, risk of transmission of other diseases from donor, expensive/not easily available, SE: serum sickness (hypersensitivity reaction to other person serum)

Question 6

What causes Whooping cough, who is at risk, how does it spread and what is the course of the illness

Answer 6

-Bordetella pertussis (gram (–)coccobacillus
Risk: first year of life, household spread
Spreads: aerosol droplets via cough  respiratory tract

Present

1. Catarrhal phase (1-2 wks): runny nose, conjunctival injection, malaise
2. Paroxysmal phase (1-10wks): short expiratory burst of rapid coughs , inspiratory gasp (whoop)
3. Convalescent phase

Question 7

What are the treatment and complications of pertussis.

Answer 7

Comp: 2ndary bacterial infections eg. pneumonia
-encephalopathy, seizures, apnoea

Treat: Azithromycin: may shorten illness if started early in the first few weeks, but does little in established illness. Decreases infectivity

Question 8

How has the acellular vaccine changed the epidemiology of Whooping cough vs old vaccine and who is eligible for vax

Answer 8

Original vax: whole cell vaccine which had local and systemic reactions

Acellular vax contains virulence factors but needs 3 dose primary schedule = protect 4-6 yrs
2 Booster doses: prolonged protection 6-10 yrs

However if no additional booster, immunity wanes and susceptible adults become a reservoir of pertussis to infect infants
Therefore Adults living/working w young children eg. teacher, healthcare, childcare eligible for vaccine

Question 9

What is polio(myelitis) caused by, who is at risk, the disease course

Answer 9

Poliovirus: destroys LMN resulting in irreversible paralysis – generally limbs but there is respiratory failure death.

Risk: children under 5 affected, endemic to Afghanistan and Pakistan

Question 10

Compare the 2 polio vaccines -which one do we use now

Answer 10

1st used Live Oral poliovirus vaccine where there is endemic disease – 1 dose = immunisation
-colonises the gut causing intestinal immunity.

However switch to Inactivated polio vaccine due to rare vaccine associated paralytic polio disease 1/2.4 mil.

IAP: 99% effective with 3 dose course, most countries changed to this now