Lecture 10.2: Vaccinations

Question 1

What are the Methods of Acquiring Immunity?

Answer 1

Active: Natural (Infection) and Artificial (Immunisation)
Passive: Natural (Maternal) and Artificial (External Antibodies)

Question 2

When should you NOT be vaccinated?

Answer 2

• Allergy
• Fever
• HIV infection
• Immunodeficiency
• IG administration
• Neurological disorder
• Prematurity
• Reactions to Previous vaccine
• Simultaneous Administration of Vaccines
• Thrombocytopenia

Question 3

What is Herd Immunity?

Answer 3

Population immunity is the state achieved when immunisation programmes reach sufficiently high coverage of the target population to interrupt transmission within the community

Question 4

What Factors affect Herd Immunity? (4)

Answer 4

• Degree to which disease is infectious
• Efficacy of vaccines
• Vulnerability of population
• Environmental factors

Question 5

What are some Issues with Herd Immunity?

Answer 5

• Protects people unable to be vaccinated (age, have health problems, pregnant)
• Thresholds (% of population that needs to be immune) are quite high (80-100%)

Question 6

Characteristics of a Good Vaccine (8)

Answer 6

• Safe
• Few side effects
• Give long lasting, appropriate protection
• Low in cost
• Stable with long shelf life (no special
storage requirements)
• Easy to administer
• Inexpensive
• Public must see more benefit than risk

Question 7

What is Poliomyelitis?

Answer 7

• A viral disease caused by poliovirus
• It may affect the spinal cord causing muscle weakness and paralysis

Question 8

How does Poliovirus enter the body?

Answer 8

• The virus enters the body through the mouth
• Usually from hands contaminated of an infected person

Question 9

What are the 3 Types of Polio?

Answer 9

• Spinal
• Bulbar
• Bulbospinal

Question 10

When does Polio cause paralysis?

Answer 10

It is primarily an intestinal infection that causes paralysis in less than 1% of cases

Question 11

Inactivated Polio Vaccine (IPV) SALK: What is it? Pros?

Answer 11

• Whole Agent Vaccines (virus killed using heat/formaldehyde)
• Reduced incidence of polio by c.90% within two years (children + families)
• Long-lasting immunity to all 3 poliovirus types
• The virus is not live, thus it is easier to manage than OPV

Question 12

Inactivated Polio Vaccine (IPV) SALK: Cons?

Answer 12

• The price of IPV is over 5 times that of OPV
• IPV induces only little immunity in intestinal tract

Question 13

Oral Polio Vaccine (OPV) - Sabin: What is it? Pros?

Answer 13

• Whole Agent Vaccines/Attenuated (lessens the virulence of a microbe)
• Easily administered by giving children a sugar cube/liquid containing the
vaccine
• Indirectly protects other susceptible individuals by secondary vaccination

Question 14

Oral Polio Vaccine (OPV) - Sabin: Cons?

Answer 14

• The risk of vaccine
• Associated paralytic polio as a result of the vaccination

Question 15

Attenuation of Viruses by Passage through Non-Human Cells (4 Steps)

Answer 15

1) Pathogenic virus isolated from patient, grown in human cells
2) Infect monkey cells with cultured virus
3) Virus acquires many mutations that allow it to grow well in monkey cells
4) Mutations make the virus unable to grow well in human cells

Question 16

What type of viral vaccine required several doses?

Answer 16

Killed virus vaccine requires multiple doses (booster shots) to adequately stimulate a protective immune response

Question 17

What type of viral vaccine only requires 1 does?

Answer 17

• Live virus vaccines replicate in the host.
• No requirement for boosters

Question 18

Advantages of Live Vaccines? (3)

Answer 18

• Multiply like natural organism
• Require fewer doses and boosters
• Long-lasting

Question 19

Disadvantages of Live Vaccines? (3)

Answer 19

• Special storage
• Back mutation
• Side effects

Question 20

What are Toxoid Vaccines?

Answer 20

• Vaccines which consist of exotoxins that have been inactivated, either by heat
or chemicals
• Toxoid consists of weakened components or toxins secreted by the pathogens
• These vaccines are intended to build immunity against the toxins
• But not necessarily the bacteria that produce the toxins

Question 21

Advantages of Toxoid Vaccines? (1)

Answer 21

• Does not cause disease

Question 22

Disadvantages of Toxoid Vaccines? (2)

Answer 22

• Not highly immunogenic
• May require multiple doses

Question 23

What are Subunit Vaccines?

Answer 23

• Subunit vaccines, do not contain live components of the pathogen
• They differ from inactivated whole-cell vaccines
• They contain only the antigenic parts of the pathogen

Question 24

Types of Subunit Vaccines (3)

Answer 24

1) Protein based
2) Polysaccharide
3) Conjugate

Question 25

Subunit Vaccines: Protein Based Vaccine

Answer 25

• A specific isolated protein of the pathogen is used
• Con: If protein denatured, immune response may be inadequate
• Acellular Pertussis (inactivated pertussis toxin + bacterial components)
• Hepatitis B vaccine ( Hepatitis B surface Antigen HBsAg )

Question 26

Subunit Vaccines: Polysaccharide Vaccine

Answer 26

• Polysaccharide from cell wall of bacteria is used
• Con: T-cell independent (Stimulate B cells without stimulating T Helper cells)
• Con: Poor immune response in < 2 years age
• Con: Only Short term immunity (No immune memory)
• Con: No booster response even after repeated injections
• Typhoid Vi Polysaccharide Vaccine
• Pneumococcal Polysaccharide Vaccine

Question 27

Subunit Vaccines: Conjugate Vaccine

Answer 27

• Polysaccharide from bacterial cell wall used + Carrier Protein (Conjugation)
• T Cell Independent –> T Cell DEPENDENT immunity
• Increased Immune response <2years age
• Booster response to multiple doses

Question 28

How to Overcome Subunit Vaccine problems?

Answer 28

1) Multiple doses (booster shots)
2) Use adjuvants
• Prolongs stimulation of immune response
• Works by trapping the antigens in a chemical complex and releases them
slowly

Question 29

What are Adjuvents?

Answer 29

An ingredient used in some vaccines that helps create a stronger immune response in people receiving the vaccine

Question 30

Examples of Adjuvents

Answer 30

• Aluminium Salts (DTaP, Hib, HepA, HepB, HPV, MMR, rabies, rotavirus, rubella,
varicella)
• Monophosphoryl lipid A (HPV-cervarix)

Question 31

What are DNA Vaccines?

Answer 31

• Create a recombinant plasmid containing a gene encoding a specific antigen

Question 32

What are Recombinant Vaccines?

Answer 32

Recombinant vaccines are products of genetic engineering
Where a harmless agent such as yeast, is programed to produce antigens of harmful pathogens

Question 33

What are mRNA Vaccines? Specifically the COVID-19 Vaccine?

Answer 33

• It contains the genetic sequence (mRNA) for the spike protein which is found on
the surface of the SARS-CoV-2 virus
• Wrapped in a lipid envelope (referred to as a nanoparticle) to enable it to be
transported into the cells in the body

Question 34

How do mRNA vaccines work? Specifically the COVID-19 Vaccine?

Answer 34

• When injected, the mRNA is taken up by the host’s cells which translate the
genetic information and produce the spike proteins
• These are then displayed on the surface of the cell
• This stimulates the immune system to produce antibodies and activate T-cells
• This prepares the immune system to respond to any future exposure to the
SARS-CoV-2 virus by binding to and disabling any virus encountered
• As no whole/live virus involved, the vaccine cannot cause disease
• The mRNA naturally degrades after a few days

Question 35

AstraZeneca COVID-19 Vaccine

Answer 35

• A viral vector vaccine
• Uses a weakened adenovirus as a carrier to deliver the SARS-CoV-2 antigen
• The adenovirus has been modified so that it cannot replicate in human cells • Thus cannot cause any disease
• The genes that encode for the spike protein on the SARS-CoV-2 virus have
been inserted into the adenovirus’s genetic code to make the vaccine
• When the vaccine is injected, it enters the host’s cells which then manufacture
the spike protein
• This then stimulates the immune system which reacts by producing antibodies
and memory cells to the SARS-CoV-2 virus without causing disease

Question 36

Routes of Administration of Vaccines (5)

Answer 36

• Deep subcutaneous or intramuscular route (most vaccines)
• Oral route (oral BCG vaccine)
• Intradermal route (BCG vaccine)
• Scarification (small pox vaccine)
• Intranasal route (live attenuated influenza vaccine)