Vaccines work by exposing the immune system to weakened or killed forms of pathogens to stimulate antibody production against them. There are several types of vaccines including live attenuated vaccines using weakened live pathogens, inactivated vaccines using killed pathogens, subunit vaccines using pathogen proteins, DNA vaccines using genetic material, synthetic peptide vaccines, and toxoid vaccines using inactivated bacterial toxins. Vaccines provide active immunity and are the most effective method of preventing infectious diseases.

1. Dr. P. Saranraj
Head
Department of Microbiology
Sacred Heart College (Autonomous)
Tirupattur – 635 601
Tamil Nadu, India
Mobile: +91-9994146964; E.mail:
microsaranraj@gmail.com
VACCINES

2. VACCINES
 Vaccine, is a suspension of weakened, killed, or
fragmented microbes or toxins or
of antibodies or lymphocytes that is
administered primarily to prevent disease.
 A vaccine can confer Active immunity
(Artificial active immunity) against a specific
harmful agent by stimulating the Immune
system to attack the agent.
 The term ''vaccine'' was derived in 1796 from the
Edward Jenner's use of the term ''Cow pox''
(Latin '‘variolae vaccinia'').
 Edward Jenner was the pioneer of using Cow
pox pustules to prevent small pox infections

3.  Vaccines can be Prophylactic (example: to
prevent or ameliorate the effects of a
future infection by a natural or
"wild" pathogen),
or Therapeutic (e.g., vaccines against
cancer are being investigated).
 The administration of vaccines is
called Vaccination. Vaccination is the most
effective method of preventing infectious
diseases.
 Vaccination given during childhood is
generally safe.
 Adverse effects if any are generally mild.

4. LIVE ATTENUATED VACCINES
 Live Attenuated Vaccine (LAV) - A vaccine
prepared from living microorganisms that have been
weakened under laboratory conditions (Tissue
culture, Embryonated eggs and Live animals). They
will grow and replicate in a vaccinated
individual, but because they are weak, they will
cause no or very mild disease.
 Examples - Viral: Measles, Mumps & Rubella
(MMR) (Combined vaccine) vaccine, Influenza
vaccine (nasal spray), Chicken pox
vaccine, Smallpox vaccine, Oral Adenovirus
vaccine, Oral Polio vaccine (Sabin), Rotavirus
vaccine, Shingles vaccine and Yellow fever vaccine.
Bacterial: Bacillus Calmette – Guerin (BCG)

5. Administration of Attenuated Vaccines
 In an Attenuated vaccine, live virus particles
with very low virulence are administered.
They will reproduce, but very slowly. Since they
do reproduce and continue to present antigen
beyond the initial vaccination, boosters are
required less often (Adjuvants).
 These vaccines are produced by growing the
virus in Tissue cultures that will select for less
virulent strains, or by Mutagenesis or Targeted
deletions in genes required for virulence. There
is a small risk of reversion to virulence; this
risk is smaller in vaccines with deletions.
 Attenuated vaccines also cannot be used

6. Advantages of Attenuated Vaccines
 Activates all phases of the Immune system (for
instance IgA local antibodies are produced).
 Provides more durable immunity; boosters are
required less frequently (except OPV).
 Low cost and Quick immunity.
 Easy to administer (for
instance OPV for Polio can be taken orally,
rather than requiring a sterile injection by a
trained health worker, as the inactivated form IPV
dose).
 Vaccines have strong beneficial Non-specific
effects (The effects which go beyond the
specific protective effects against the targeted

7. Disadvantages of Attenuated Vaccines
 Secondary mutation can cause a reversion to
virulence. For this reason, OPV is no longer used
in the United States, and has been replaced on
the Recommended Childhood Immunization
Schedule by the Inactivated polio vaccine (IPV).
 Severe complications
in Immunocompromised patients.
 Some can be difficult to transport due to
requirement to maintain conditions
(e.g. temperature)

8. INACTIVATED OR KILLED VACCINES
 Vaccines of this type are created by
inactivating a pathogen, typically using
heat or chemicals such as formaldehyde
or formalin. This destroys the pathogen’s
ability to replicate, but keeps it “intact” so
that the immune system can still recognize
it.
 Example – Virus: Polio vaccine (Salk
vaccine), Hepatitis A vaccine, Rabies
vaccine, Japanese Encephalitis vaccine and
Influenza vaccine. Bacteria: Inactivated
Typhoid vaccine, Inactivated Cholera

9.  Inactivated vaccines are further classified
depending on the method used to
inactivate the virus. They are (i) Whole
virus and vaccines, (ii) Split virus vaccines.
(i) Whole virus vaccines use the entire
virus particle, fully destroyed using heat,
chemicals, or radiation.
(ii) Split virus vaccines are produced by
using a detergent to disrupt the virus.

10. SUBUNIT VACCINE
 Subunit vaccines are vaccines that use only
part of the disease-causing virus.
 One part of the virus is responsible for
creating disease. The part responsible for
creating disease is a protein, which we call
the antigen. Subunit vaccines can contain from
1 to 20 antigens, that are either taken directly
from the virus, or grown in the lab using the virus
DNA.
 Some of the commonly used Subunit vaccines –
Bacteria: Acellular Pertussis vaccine. Virus:
Hepatitis B Vaccine and Human Papiloma Virus
(HPV) vaccine.

11.  An example of the Recombinant subunit vaccine
is the Hepatitis B virus vaccine. The Hepatitis
B genes that code for the antigens were inserted
into common Baker’s yeast. That yeast grew and
expressed the genes and produced the antigen
protein. Scientists were then able to collect and
purify the protein antigen, which was used for the
vaccine.
 Vi capsular polysaccharide vaccine (ViCPS) is
another Subunit vaccine (contains
polysaccharide linked to the Vi capsular antigen),
in this case, against Typhoid caused by the Typhi
serotype of Salmonella. It is also called a
Conjugate vaccine, in which a polysaccharide

12. Advantages of Subunit Vaccines
 Subunit vaccines can be given to people
with weakened immune systems.
 These vaccines appear to give long-lived
immunity.
 Since only parts of the virus are used for these
vaccines, the risks of reactions are very low.
Disadvantages of Subunit Vaccines
 Several doses must be given for proper life-long
immunity

13. DNA VACCINE
 DNA vaccination is a technique for protecting
against disease by injection with genetically
engineered DNA (Plasmid DNA) so cells directly
produce an antigen, producing a
protective immunological response.
 Muscle cells take up the DNA and the encoded
protein antigen is expressed, leading to both a
Humoral antibody response and a Cell-mediated
response.
 Several DNA vaccines are available
for Veterinary use. Currently no DNA vaccines
have been approved for human use.
 A veterinary DNA vaccine to

14.  An improved method for administering these
vaccines entails coating microscopic gold beads
with the plasmid DNA and then delivering the
coated particles through the skin into the
underlying muscle with an air gun (called a Gene
gun). This will allow rapid delivery of a vaccine to
large populations without the requirement for
huge supplies of needles and syringes.
 Research of DNA Vaccine is underway
for viral, bacterial and parasitic diseases in
humans, as well as for several cancers.

15. Advantages of DNA Vaccines
 No risk for infection
 Antigen presentation by both MHC molecules
 Ease of development and production
 Stability for storage and shipping
 Long-term persistence of immunogen
 Encoded protein is expressed in the host in its natural
form - there is no denaturation or modification.
 Refrigeration is not required for the handling and storage
of the plasmid DNA, a feature that greatly lowers the cost
and complexity of delivery.
 DNA vaccines also induce both Humoral and Cell-
mediated immunity.
 DNA vaccines cause prolonged expression of the
antigen, which generates significant immunological

16. Disadvantages of DNA Vaccines
 Limited to protein immunogens (not useful for
non-protein based antigens such as bacterial
polysaccharides)
 Risk of affecting genes controlling cell growth
 Possibility of inducing antibody production
against DNA
 Possibility of tolerance to the antigen (protein)
produced
 Potential for atypical processing of bacterial and
parasite proteins

17. SYNTHETIC PEPTIDE VACCINE
 Synthetic peptide vaccine is
a vaccine consisting mainly of 20 to 30
synthetic peptides.
 Synthetic peptide vaccine are usually considered
to be safer than vaccines from microbial cultures.
Creating vaccines synthetically has the ability to
increase the speed of production. This is
especially important in the event of a pandemic.
 The world's first synthetic vaccine was created in
1982 from Diphtheria toxin by Louis Chedid
(scientist) from the Pasteur Institute (Paris,
France) and Michael Sela from the Weizmann
Institute (Rehovot, Israel).

18. Advantages of Synthetic peptide Vaccines
 Antigens are precisely defined and free from
unnecessary components which may be
associated with side effects.
 Stable and relatively cheap to manufacture.
 Less quality assurance is required.
 Changes due to natural variation of the virus can
be readily accommodated, which would be a
great advantage for unstable viruses such as
influenza.
 Less toxic.
 Production and quality control is very simple.

19. Disadvantages of Synthetic Peptide Vaccines
 Synthetic peptides do not readily stimulate T
cells.
 Synthetic peptides are not applicable to all
viruses.
 May be less immunogenic than conventional
inactivated whole - virus vaccines.
 Requires Adjuvant
 Fails to elicit Cell Mediated Immunity

20. ANTI-IDIOTYPE VACCINE
 A vaccine made of antibodies that see other
antibodies as the antigen and bind to it.
 Anti-idiotype vaccines can stimulate the body to
produce antibodies against tumor cells.
 Anti-idiotype antibody(AId) is the anti-antibody
aiming at group-specific antigen Epitope of the V
region of the antibody molecule.
 Anti-idiotypic
vaccines comprise antibodies that have 3D
immunogenic regions, designated idiotopes, that
consist of protein sequences that bind to cell
receptors. Idiotopes are aggregated
into idiotypes specific of their target antigen. An

21.  Anti-idiotype antibody vaccine is a new type of
immune biologics which was developed in the
late 1970s. It developed towards practical areas
and it had a big through in its production of
vaccines, treatment of cancer and so on.
 Anti-idiotypes have many potential uses as viral
vaccines, particularly when the antigen is difficult
to grow or hazardous. They have been used to
induce immunity against a wide range of viruses,
including Hepatitis – B, Rabies, Newcastle
disease virus and Reoviruses and Polioviruses.

22. VACCINATION SCHEDULE

23. TOXOIDS
 Toxoid vaccines are vaccines that are made
from the toxins (harmful chemicals) from
bacteria.
 Some bacteria that cause disease through
releasing a protein called a toxin. Scientists
can inactivate these toxins in the lab using a
chemical called formalin and sterilized water,
which are completely safe to use in small
quantities in the human body.
 Once the toxin is inactivated, it’s called a
toxoid, and it can no longer cause harm. The
body learns how to fight off the bacteria’s natural
toxin once exposed to the toxoid through

24.  In international medical literature, the Toxoid
preparation also is known
as Anatoxin or Anatoxine.
 Example for Toxoids or Toxoid vaccines -
Diphtheria toxoid, Tetanus
toxoid and Botulism toxoid.
 Toxoids can actually be considered killed or
inactivated vaccines, but are sometimes given
their own category to highlight the fact that they
contain an inactivated toxin, and not an
inactivated form of bacteria.