Immunisation Flashcards
Define immunisation
The process where a susceptible individual is rendered immune to an infection.
Describe the immune response following immunisation.
- Vaccines take advantage of the active immune system’s ability toremember an infection through memory B cells.
- Vaccine is injected & immune system recognises & responds to it by producing pro-inflammatory cytokines & pro-inflammatory chemokines which attract immune cells to the site of injection.
- Dendritic cells recognise PAMPs. Dendritic cells take up & present the antigens on their surface & migrate towards the lymph nodes.
- At lymph nodes, Dendritic cells interact w/ Cytotoxic T Cells (CD8) & Helper T Cells (CD4).
- T Helper Cells assist w/ differentiation of naive B Cells to produce Memory B Cells
What is active immunity? What is passive immunity?
Passive - preformed antibodies from another individual, giving temporary protection.
- Mother will pass IgG antibodies across placenta & through breast milk.
- You can give immunoglobulins which are taken from donors* (people who have already had the disease or vaccine).
Active - involves the person’s immune system - longer lasting & involves memory.
Types of active vaccines?
Live attenuated vaccines
Inactivated whole cell vaccines
mRNA
Viral vector
Inactivated toxin
Subunit recombinant proteins
Subunit chemically purified
Polysaccharides
Conjugated polysaccharides
What are live attenuated vaccines? Examples? Pros & cons? Who is it not suitable for?
Pathogen is capable of replicating but is in weakened state.
- Attenuated by serial passage through tissue culture or an animal model - becomes more adapted to these environments & less adapted to cause illness in humans.
Examples:
- Rotavirus vaccine
- MMR vaccine
- Influenza vaccine
- Shingles vaccine
- Chickenpox vaccine (varicella zoster)
- BCG vaccine against TB
- Yellow fever vaccine
- Oral typhoid vaccine (not the injected vaccine)
- Oral polio vaccine
Pros:
- Pathogen replicates in recipient = strong & memorable immune response = fewer doses.
- More closely resembles natural infection.
Cons:
- Potential for reversion - a mutated version can become the full version
- Potential for sustained vaccine strain infection
- Vaccine that is live can be spread in faeces
Not suitable for:
1. Immunocompromised patients
2. Pregnant women - risk of live vaccine crossing the placenta & infecting the baby!!
What are Inactivated whole cell vaccines? Examples? Pros vs Cons?
Grow pathogen then kill it by chemical or physical processes
Examples:
- Hepatitis A
- Polio
- Rabies
- Inactivated polio (Salk)
Pros:
- Cannot cause disease because pathogen is dead.
- Can be given to immunocompromised patients.
Con:
-Doesn’t usually provide protection that is as strong as live vaccines, so several booster jabs could be required.
How do mRNA vaccines work? Examples?
mRNA from vaccine is translated into antigen proteins when inside the cell.
- stimulates an immune response.
Examples
- Pfizer BioNTech COVID-19
- ModernaCOVID-19
What are viral vector vaccines? Examples?
Modified version of a different virus is used to trigger an immune response.
- works by attaching target antigens onto a host which is unable to cause disease in humans.
Example
-AstraZenecaCOVID-19
What is an inactivated toxin vaccine? Examples?
Toxins from bacteria are chemically treated to eliminate toxicity whilst maintaining immunogenicity.
Examples
- Diphtheria
- Pertussis
What are subunit recombinant proteins? Examples? Pros vs cons?
Specific viral protein (antigen) is produced in either yeast or insect cell systems.
Examples
- Hepatitis B
- Human Papillomavirus (HPV)
- Meningitis B
Pros:
- only injecting the antigen so vaccine can’t cause disease.
Cons:
- don’t have such long lasting immunity as live vaccines.
- Require adjuvants which strengthen & lengthen immune response, increasing chance of sore arm.
What are Subunit chemically purified vaccines? Examples?
components of a pathogen are purified for use in a vaccine
Example
- Influenza
What are polysaccharide vaccines? Examples? Pros vs cons?
Purified bacterial polysaccharide.
Examples
- Some meningococcal vaccines
- Some pneumococcal vaccines
- Salmonella
cons
- Produce poor immune response in young children.
- B cell receptors link when attaching to polysaccharide & produce a plasma cell that makes antibodies-doesn’t involve any T-cells so response is smaller
What are conjugated polysaccharide vaccines? Examples? Pro?
Purified bacterial polysaccharide linked to a protein conjuagte.
- Usually diptheria or tetnus toxin.
Examples
- Haemophilus Influenzae type b (Hib)
- Pneumococcal
- Meningococcal e.g. MenC & MenACYW
Pros
- T-cell dependent response = gives memory response = last longer & works for children.
What are adjuvants?
Agents that stimulate the immune system
e.g. Aluminium phosphate & hydroxide
Thought to sequester antigen & cause inflammation = attracting immune cells.
How are vaccines most commonly used? Who gets which vaccines?
Prophylaxis - pre-exposure
Children - according to the UK vaccine schedule.
Adults:
- 65 yrs - flu vaccine every year
- 65 yrs - pneumococcal
- 70 yrs - varicella zoster (shingles vaccine)
Pregnant women - flu vaccine & pertussis (whooping cough) from 16 week gestation - mainly given to provide passive immunity to baby- were getting whooping cough when they were too young to be vaccinated.
Adults & children at high risk due to underlying health conditions.
Those at risk due to occupation, lifestyle or contacts
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