Lecture 10.2: Vaccinations Flashcards
What are the Methods of Acquiring Immunity?
Active: Natural (Infection) and Artificial (Immunisation)
Passive: Natural (Maternal) and Artificial (External Antibodies)
When should you NOT be vaccinated?
• Allergy
• Fever
• HIV infection
• Immunodeficiency
• IG administration
• Neurological disorder
• Prematurity
• Reactions to Previous vaccine
• Simultaneous Administration of Vaccines
• Thrombocytopenia
What is Herd Immunity?
Population immunity is the state achieved when immunisation programmes reach sufficiently high coverage of the target population to interrupt transmission within the community
What Factors affect Herd Immunity? (4)
• Degree to which disease is infectious
• Efficacy of vaccines
• Vulnerability of population
• Environmental factors
What are some Issues with Herd Immunity?
• Protects people unable to be vaccinated (age, have health problems, pregnant)
• Thresholds (% of population that needs to be immune) are quite high (80-100%)
Characteristics of a Good Vaccine (8)
• 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
What is Poliomyelitis?
• A viral disease caused by poliovirus
• It may affect the spinal cord causing muscle weakness and paralysis
How does Poliovirus enter the body?
• The virus enters the body through the mouth
• Usually from hands contaminated of an infected person
What are the 3 Types of Polio?
• Spinal
• Bulbar
• Bulbospinal
When does Polio cause paralysis?
It is primarily an intestinal infection that causes paralysis in less than 1% of cases
Inactivated Polio Vaccine (IPV) SALK: What is it? Pros?
• 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
Inactivated Polio Vaccine (IPV) SALK: Cons?
• The price of IPV is over 5 times that of OPV
• IPV induces only little immunity in intestinal tract
Oral Polio Vaccine (OPV) - Sabin: What is it? Pros?
• 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
Oral Polio Vaccine (OPV) - Sabin: Cons?
• The risk of vaccine
• Associated paralytic polio as a result of the vaccination
Attenuation of Viruses by Passage through Non-Human Cells (4 Steps)
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
What type of viral vaccine required several doses?
Killed virus vaccine requires multiple doses (booster shots) to adequately stimulate a protective immune response
What type of viral vaccine only requires 1 does?
• Live virus vaccines replicate in the host.
• No requirement for boosters
Advantages of Live Vaccines? (3)
• Multiply like natural organism
• Require fewer doses and boosters
• Long-lasting
Disadvantages of Live Vaccines? (3)
• Special storage
• Back mutation
• Side effects
What are Toxoid Vaccines?
• 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
Advantages of Toxoid Vaccines? (1)
• Does not cause disease
Disadvantages of Toxoid Vaccines? (2)
• Not highly immunogenic
• May require multiple doses
What are Subunit Vaccines?
• 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
Types of Subunit Vaccines (3)
1) Protein based
2) Polysaccharide
3) Conjugate
Subunit Vaccines: Protein Based Vaccine
• 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 )
Subunit Vaccines: Polysaccharide Vaccine
• 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
Subunit Vaccines: Conjugate Vaccine
• 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
How to Overcome Subunit Vaccine problems?
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
What are Adjuvents?
An ingredient used in some vaccines that helps create a stronger immune response in people receiving the vaccine
Examples of Adjuvents
• Aluminium Salts (DTaP, Hib, HepA, HepB, HPV, MMR, rabies, rotavirus, rubella,
varicella)
• Monophosphoryl lipid A (HPV-cervarix)
What are DNA Vaccines?
• Create a recombinant plasmid containing a gene encoding a specific antigen
What are Recombinant Vaccines?
Recombinant vaccines are products of genetic engineering
Where a harmless agent such as yeast, is programed to produce antigens of harmful pathogens
What are mRNA Vaccines? Specifically the COVID-19 Vaccine?
• 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
How do mRNA vaccines work? Specifically the COVID-19 Vaccine?
• 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
AstraZeneca COVID-19 Vaccine
• 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
Routes of Administration of Vaccines (5)
• 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)
