Vaccinology

1. Vaccines:
Basic vaccinology
Dr SO Ogundele

2. Background
• Viral infections are responsible for many human diseases, from
common diseases like the flu to emerging infections such as Zika virus
and SARS-CoV-2
• Vaccines are biological products that can be used to safely induce an
immune response that confers protection against infection and/or
disease on subsequent exposure to a pathogen
• “Vaccinology,” encompases vaccine development as well as the use of
vaccines and their effects on public health
• WHO estimates that 2–3million lives are saved each year by current
immunization programmes

3. Background
• To achieve immunization, vaccine must contain antigens that are
either derived from the pathogen or produced synthetically to
represent components of the pathogen
• Essential component of most vaccines is one or more protein antigens
that induce immune responses that provide protection
• Polysaccharide antigens can also induce protective immune responses
and are the basis of vaccines that have been developed to prevent
several bacterial infections, such as pneumonia and meningitis caused
by Streptococcus pneumoniae

4. Note!
•Vaccination≠ Immunization!!!

5. History
• During late 1760s , British physician Edward Jenner who was then an
apprentice surgeon learned of the story that dairy workers usually do
not suffer from samll pox because they are protected by previous
exposure to cow pox which is a milder and less deadly disease in
humans
• In 1796 Jenner took part of the Cow pus virus (variola vaccinia) from
the pus from the hand of a milk maid who had cow pox and rub it
unto a 8 year old boy, 6 weeks later he innoculated the boy with small
pox
• He observed that the boy did not develop small pox, he carried out
similar test in few other people

6. History
• The word vaccine was coined from the latin word for cow pox (variola
vaccinia)
• In 1798 he reported that his vaccine was safe in adults and children
and prevent against contracting small pox
• Second generation vaccines were introduced in 1880 by Louis Pastuer
who developed vaccines for chicken cholera and anthrax
• From late 19th century vaccines were considered as a matter of
national pride and compulsory vaccination laws were enacted

7. Types of vaccines
• Whole organism vaccines
• Killed (inactivated)
• Live attenuated
• Purified macromolecules as vaccines
• Toxoids
• Capsular polysaccharides
• Recombinant microbial antigens/surface antigens
• Recombinant vector vaccines
• Nucleic acid vaccines
• Multivalent subunit vaccines

8. Whole oragism vaccines
• Whole virus vaccines use a weakened (attenuated) or deactivated form of
the pathogen that causes a disease to trigger protective immunity to it
• Live vaccines may have the potential to replicate in an uncontrolled
manner in immunocompromised individuals
• E.g, children with some primary immunodeficiency,
• individuals with HIV infection
• those receiving immunosuppressive drugs
• Leading to some restrictions to their use
• Non-live vaccines pose no risk to immunocompromised individuals
• they may not confer protection in those with B cell or combined immunodeficiency,

9. Killed (inactivated) vaccines
• This type of vaccine contained killed but previosly virulent micro-organsim
that are produced under conditions that are destructive such as chemical,
heat, radioactivity or antibiotics
• They are more stable and safer than the live attenauted vaccines
• Examples
• Anthrax
• Cholera
• Pertussis
• Plague
• Influeza
• Hepatitis A
• Polio (Salk)

10. Advantages and disadvantages of inactivated
virus vaccines
• Advantages
• Well-established technology
• Suitable for people with compromised immune systems
• No live components, so no risk of the vaccine triggering disease
• Relatively simple to manufacture
• Relatively stable
• Disadvantage
• Booster shots may be required

11. Live attenuated vaccines
• Vaccines in this class are made from live attenuated organisms. They are
the closest to natural infection
• Many are cultured under conditions that disable their virulent properties
• Some contain organisms that are closely related but less dangerous, which produce a
broad immune response that cover the virulent organism
• Examples include
• Tuberculosis
• Typhoid
• Polio (Sabin)
• Yellow fever
• Rabies
• Chicken pox (varicella zooster)
• Measles

12. Advantages and disadvantages of live
attenuated vaccines
• Advantages
• Well-established technology
• Strong immune response
• Immune response involves B cells and T cells
• Relatively simple to manufacture
• Disadvantages
• Unsuitable for people with compromised immune systems (e.g. those with
HIV and pregnant women)
• In very rare cases, live attenuated vaccines can revert to a more pathogenic
form, triggering disease in vaccinated individuals or their contacts e.g Polio
vaccine
• Relatively temperature sensitive, so careful storage necessary

13. Toxoids/inactivated exotoxins
• These are for bacterial that secret toxins or harmful chemicals
• Toxoids are vaccines that contain exotoxins which have been
inactivated either by chemical or heat
• Detoxified toxins are called toxoids
• They are meant to produce immunity against toxins but not
neccesarily against the organisms that produce the toxins
• Examples
• Botulinum antotixin
• Diphtheria antitoxin

14. Capsular polysaccharides
• Some bateria possess outer coating of polysaccharide (sugar
molecule), this disguise the bacteria antigen so that immune system
of infants and younger children do not recognise them
• Virulence of some bacterial depends primarily on the phagocytic
properties of their hydrophilic polysaccharide capsules
• Coating the capsules with antibodies and or complement increases
the ability of the macrophages and neutrophils to phagocyte such
pathogens
• Vaccine for Streptococcus Pneumonia consists of 23 antigenically
different polysaccharide capsules

15. Recombinant microbial antigen/surface
antigen
• Genes encoding any immunogenic protein can be cloned and then
expresssed in bacteria, yeast or human cells using recombinant DNA
technology
• Hepatitis B vaccine is an example of this
• The vaccine was developed by cloning the gene for the major surface
antigen of hepatitis B (HBsAg) and expressing it in yeast cells

16. Nucleic acid vaccines
• Nucleic acid vaccines use genetic material from a disease-causing
virus or bacterium (a pathogen) to stimulate an immune response
against it
• Depending on the vaccine, the genetic material could be DNA or RNA
• In both cases it provides the instructions for making a specific protein
from the pathogen, which the immune system will recognize as
foreign (an antigen)
• These vaccines dispenses with both the whole organsim and its parts
• Example
• Pfizer covid-19 vaccine

17. Advantages and disadvantages of nucleic acid
vaccines
• Advantages
• Immune response involves B cells and T cells
• No live components, so no risk of the vaccine triggering disease
• Relatively easy to manufacture
• Disadvantage
• Some RNA vaccines require ultra-cold storage
• Booster shots may be required

18. Recombinant vector vaccines
• Viral vector-based vaccines differ from most conventional vaccines in that
they don’t actually contain antigens, but rather use the body’s own cells to
produce them
• They do this by using a modified virus (the vector) to deliver genetic code
for antigen
• They are similar to the DNA vaccines
• They use attenuated virus or bacterium to introduce microbial DNA to cells
of the body
• Vector refers to virus bacterium used as the carrier
• Example
• DPT, rVSV-ZEBOV vaccine against Ebola

19. Vaccines adjuvants
• Adjuvants (Latin: adiuvare-to aid) are pharmacological or
immunological materials that modifythe effects of other agents, such
as drugs or vaccines
• They are often added to vaccines to enhance the receipient’s immune
response to antigens thus keeping injected foreign agents to a
minimum

20. Risks associated with vaccines
• Live attenuated vaccines can cause illnesses in the receipients
• Vaccines may act as super antigen causing overstimulation of the
immune system
• Individuals may may develop allergic reaction to vaccines especially if
they are produced in embryonated chicken eggs or in transgenic
plants

21. Covid-19 vaccines
• The University of Oxford/AstraZeneca vaccine
• The vaccine was developed using the viral vector technology to protect
against COVID-19
• This type of vaccine uses an unrelated harmless virus (the viral vector) to
deliver SARS-CoV-2 genetic material
• When administered, our cells use the genetic material to produce a specific
viral protein, which is recognised by our immune system and triggers a
response
• This response builds immune memory, so your body can fight off the virus in
future
• Janssen/Johnson and Johnson vaccine also use this type of technology

22. Covid-19 vaccines
• The Moderna and Pfizer/BioNTech COVID-19 vaccines
• Genetic technology was used to develop these vaccines
• The vaccines contains a segment of genetic material of the SARS-CoV-2 virus,
which causes COVID-19
• The genetic material, RNA in the case of Moderna and
Pfizer/BioNTech vaccine, codes for a specific viral protein
• When administered, human cells use the genetic material from the vaccines
to make the protein, which is recognised by the immune system and triggers a
specific response
• This response builds immune memory, so that vaccineted individuals can fight
off SARS-CoV-2 in future

23. Passive immunity
• It has been clearly established that intramuscular or intravenous
infusion of exogenous antibodies can provide protection against some
infections
• The most obvious example is that of passive transfer of maternal
antibodies across the placenta, which provides newborn infants with
protection against a wide variety of pathogens
• Use of specific neutralizing antibodies purified from immune donors
to prevent the transmission of various viruses, including varicella
zoster virus, HBV and measles
• Individuals with inherited antibody deficiency are without defence
against serious viral and bacterial infections may benefit from this

24. Summary!
• History of vaccines
• Types of vaccines
• Current application in covid-19