MI: 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
What are the main immunological targets of vaccines?
Lymphocytes and antibody production
Which other 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’s an inactivated vaccine?
Inactivated
- Whole organism is detroyed (using heat, radiation or antibiotics)
- NO risk of causing infection in the host
- Immune response may not be particularly strong or long-lasting
What’s a live attenuated vaccine
Live attenuated
- Live organisms are modified to be less virulent
- Risk of acquiring virulence
- Should be avoided in pregnant women and immunocompromised patients
- Eg. MMR
What’s a toxoid vaccine?
Toxoid
- Inactivated toxin components
- eg. Tetanus or Diptheria
What’s a subunit vaccine?
Subunit
- Protein components of the microorganisms or synthetic virus-like particles
- Lack genetic material and are unable to replicate
- eg. Hep B, HPV
What’s a conjugate vaccine?
Conjugate
- Poorly immunogenic antigens are paired with a protein that is highly immunogenic (adjuvant)
What’s a heterotypic vaccine?
Heterotypic
- Using pathogens that infect other animals but do NOT cause disease in humans
List some examples of the following types of vaccines:
- Inactivated
- Live attenuated
- Toxoid
- Subunit
- Conjugate
- Heterotypic
-
Inactivated
- Influenza
- Polio
- Cholera
-
Live attenuated
- MMR
- Yello fever
-
Toxoid
- Diphteria
- Tetanus
-
Subunit
- Hepatitis B
- HPV
-
Conjugate
- Haemophilus influenza type B
-
Heterotypic
- BCG
What are stabilisers?
Substances that are added to the vaccine to keep it chemicall stable
What is a commonly used adjuvant?
Aluminium hydroxide
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 examples of serious reactions associated with the following vaccines:
- DTP
- Poliovirus
- Measles
- Rubella
- T/DT/Td
- Hepatitis B
-
DTP
- Encephalopathy
- Shock
- Anaphylaxis
-
Poliovirus
- Guillian-Barre syndrome
- Polio
-
Measles
- Anaphylaxis
- Thrombocytopaenia
-
Rubella
- Acute arthritis
-
T/DT/Td
- Guillian-Barre syndrome
- Brachial neuritis
- Anaphylaxis
-
Hepatitis B
- Anaphylaxis
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
When are patients with measles infectious?
4 days before rash to 4 days after rash
Mono vs Multivalent vaccines?
Cover 1 or multiple strains of pathogen
