Bacterial and viral vaccines Flashcards
- What R0 is required for a disease to be halted?
R0 < 1
R0 = number of people infected by one infectious person
- What is herd immunity?
Form of immunity that occurs when vaccination of a significant proportion of the population provides a measure of protection for individuals that are not immune
- What is the herd immunity threshold?
Threshold = 1 – 1/R0
- Describe how the immune system processes vaccines.
Antigens are picked up by antigen-presenting cells and presented to naïve T helper cells
These cells become activated and, subsequently, activate B cells to become plasma cells
The plasma cells generate antibodies that are specific to the vaccine antigen
- What are the outcomes of antibodies binding to antigen?
Neutralisation of infectivity
Antibody-dependent cellular cytotoxicity
- Which response is important for live-attenuated vaccines?
T cell response to destroy infected cells
- What are the three main types of memory cell?
Memory B cells
Memory killer T cells
Memory T helper cells
- What are protective antigens?
Microbial components that give rise to a protective immune response to future infection
What are the different types of vaccines?
a. Inactivated
Whole microorganism is destroyed (using heat, radiation or antibiotics)
NO risk of causing infection in the host
Immune response may not be particularly strong or long-lasting
b. Live attenuated
Live organisms are modified to be less virulent
Risk of acquiring virulence
Should be avoided in pregnant women and immunocompromised patients
c. Toxoid
Inactivated toxin components
d. Subunit
Protein components of the microorganism or synthetic virus-like particles
Lack genetic material and are unable to replicate
e. Conjugate
Poorly immunogenic antigens are paired with a protein that is highly immunogenic (adjuvant)
f. Heterotypic
Using pathogens that infect other animals but do NOT cause disease in humans
- List examples of the following types of vaccine:
a. Inactivated
b. Live attenuated
c. Toxoid
d. Subunit
e. Conjugate
f. Heterotypic
a. Inactivated Influenza Polio Cholera b. Live attenuated MMR Yellow fever c. Toxoid Diphtheria Tetanus d. Subunit Hepatitis B HPV e. Conjugate Haemophilus influenzae type B f. Heterotypic BCG
- Why are antibiotics sometimes mixed with vaccines?
Prevent contamination
- What are the determinants of the antibody response to a vaccine?
Vaccine type
Antigen nature
Vaccination schedule
- List some contraindications for vaccines.
Previous anaphylactic reactions
Anaphylactic reaction to egg is contraindicated with the influenza vaccine
Immunocompromised and pregnant women should not receive live attenuated vaccines
If acutely unwell on the day of vaccination
DTP is contraindicated if evidence of neurological abnormality
- List some prerequisites for successful disease eradication.
No animal reservoir
Antigenically stable pathogen with one/few strains
No latent reservoir of infection and no integration of pathogenic material into host genome
Vaccine induces a lasting immune response
High coverage of vaccination
- Describe the typical presentation of measles.
Fever
Rash (appearing 4 days after fever)
Conjunctivitis
Coryzal symptoms
