vaccine delivery systems

1. Masters of pharmacy, Pharmaceutical technology (Pharmaceutics)
Subject- Advances in drug delivery (MPT-103T)
Lesion no- 7, Vaccine delivery systems By- Drx JAYESH M RAJPUT
Points: -
1) Vaccine delivery systems
Vaccines: -
A vaccine is a biological preparation that improves immunity to a particular disease, a vaccine typically contains an
agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe,
its toxins or one of its surface proteins, a vaccine contain agent that resemble a disease. The agent stimulate the body’s
immune system to recognize foreign agent, destroy it, and keep a record of it, so that the immune system can more
easily recognize and destroy any of these micro-organisms that it later encounters, vaccines can be prophylactic (to
prevent or ameliorate the effects of a future infection by any natural or wild pathogen), or therapeutic (vaccines against
cancer). The word “vaccine” originates from the Latin variole vaccine (cowpox), which Edward Jenner demonstrated in
1978 could prevent smallpox in humans. Today the term “vaccine” applies to all biological preparations, produced
from living organisms, that enhance immunity against disease and either prevent (prophylactic vaccines) or, in some
cases, treat disease (therapeutic vaccines). Vaccines are administered in liquid form, either by injection, by oral, or by
intranasal routes, ex. Polio, hepatitis-A. Etc
 Vaccines are biological product which act by reinforcing the immunological defense of the body against
foreign agencies or their toxins
 The agent or product through which immunization is active are called immunization agents
 Active immunization is process of increasing resistance to infection where by microorganisms or product of
their activity act as a antigens and stimulate certain body cell produce a antibodies with specific protective
capacity
 Passive immunization results in intermediate protecylon of short duration is achieved by antibodies
administration
 Vaccines may be single component or mixed component vaccines
Advantages: -
 Virosomes technology is approved by the FDA for use in humans, and has a high safety profile
 Virosomes are biodegradable, biocompatible, and non-toxic
 No disease transmission risk
 No auto immunogenic or anaphylaxis
 Broadly applicable with almost all important drugs (anticancer drugs, proteins, peptides, nucleic acids,
antibodies, fungicides)
 Enables drug delivery into the cytoplasm of target cell
 Promotes fusion activity in the endolysosomal pathway
 Protects drugs against degradation

2. Disadvantages: -
 Shelf-life is too short
 Scale up related problems
 Poor quality of raw material
 Pay-load is too slow
 Absence on any data on safety of these carrier systems on chronic use
 But in recent years several solutions have been worked upon to overcome above
History of vaccines: -
The term vaccine and vaccination are derived from a Latin word variole vaccinae; the diary workers never have
the often fatal disease smallpox because they already have the cowpox. First vaccine was developed in 1878 for
small pox by Edward Jenner his innovations begun with successful use of cowpox material to create immunity
against smallpox. The second generation of vaccines was introduced in 1880s by Louis Pasteur who developed
vaccines for chicken cholera and anthrax. Jenner took the pus from the hand of a milkmaid with cow pox,
scratched it into the arm of an 8yr old boy and six weeks later inoculated (variolated) the boy with small pox, he
observed that boy did not catch smallpox.
Types of vaccines: -
Vaccines are dead or inactive organisms or purified products derived from them. The different types of vaccines
are: -

3. A) Traditional vaccines
There are 4 types of traditional vaccines they are
1) Killed whole-organisms vaccines or Killed vaccine eg. Polio, influenza, rabies, Q-fever, typhoid, cholera,
plaque, pertusis, etc
2) Live attenuated vaccines eg. Polio, measles, mumps, rubella, varicella zoster, hepatitis-A, yellow fever,
tuberculosis, etc
3) Toxoid vaccine is the modification of toxin to Toxoid, eg, Toxin ⟶Toxoid by chemical modification
4) Subunit vaccines- rather than introducing an inactivated or attenuated micro-organism to an immune system a
fragment of it can create an immune response
B) Innovative vaccines
1) Conjugate vaccines
2) Recombinant vector vaccines (DNA)
3) T-cell receptor vaccines- they show the modulation of cytokine production and improve cell mediated immunity
and are under development
4) Valence-
I. Monovalent (univalent)- used to immunize against single antigen
II. Multivalent (polyvalent)- used to immunize against two or more micro-organisms
5) Heterotypic- vaccines that are pathogens of other animals that either do not cause disease or cause mild disease
in the organism being treated
How do vaccines work?
When inactivated or weakened disease-causing microorganisms enter the body, they initiate an immune response.
This response mimics the body’s natural response to infection. But unlike disease-causing organisms, vaccines are
made of components that have limited ability, or are completely unable to cause disease.

4. Antigens
 Antigens is any substance which introduce parenterally in body simulates the production of an antibody
with it specifically and an observable manner.
 Most antigens are either proteins or large polysaccharides
 The complete antigen is able to induce antibody formation and produce a specific and observable reaction
with the antibody so produced
 The smallest unit of antigencity is known as the antigenic determinant or epitope
 The epitopic is that small area on the antigen usually consisting of four or five amino acid or
monosaccharide reduce possessing specific chemical structure electrical charge and steric configuration
capable of sensitizing an immunocyte and of reacting with its complementary site on the specific antibody
or t-cell receptor
 The combining area on the antibody molecules corresponding to epitope is called paratope
Antibodies
 Antibodies are globulin proteins (a protein family with compact globular form) therefore the term
immunoglobulin’s (Ig) for antibodies is used
 Antibodies are made in response to an antigen and can recognize and bind to the antigen
 A bacterium or virus may have several epitopes that causes the production of antibodies
 Each antibody have at least two identical sites that binds to epitopes known as antigen binding site
 The number of antigen-binding site on an antibody is called the valence of that antibody. Most human
antibodies are bivalent
Diagram of antibodies: -
2) Uptake of antigens
 The components of the disease-causing organisms or the vaccine components that
trigger the immune response are known as “antigens”. These antigens trigger the
production of “antibodies” by the immune system. Antibodies bind to corresponding
antigens and induce their destruction by other immune cells.
 The induced immune response to either a disease-causing organism to a vaccine
configures the body’s immune cells to be capable of quickly recognizing, reacting to, and
subduing the relevant disese-causing organism. When the body’s immune system is

5. subsequently exposed to a same disease-causing organism, the immune system will
contain and eliminate the infection before it can cause harm to the body.
Immunoglobulin classes
 The simplest and abundant immunoglobulins are monomer but they can also assume some difference in
sizeand arrangement
 The five classes of immunoglobulins designated are IgG, IgA, IgM, IgE, IgD.
 Each class has a different role in the immune response
Immunoglobulin class H chain
 IgG g(gamma)
 IgA a(alpha)
 IgM m(mu)
 IgD d(delta)
 IgE e(epsilon)
Antigen-antibody reaction
 Antigens and antibodies combine with each other specifically and in an observable manner
 These reaction serve several purpose
 In the body they form the basis of antibody mediate immunity in infection diseases or of tissue injury in
some types of hypersensitive and autoimmune diseases
 In the laboratory they help in the diagnosis of infections
 In the identification of infectious agents and of non-infectious antigens
 These reaction can be used for the detection and quantization of either antigen or antibodies
 Antigen-antibody reaction in vitro are known as serological reaction
 Both participate in the formation of agglutinate and precipitates
 Antigens and antibodies can combine in varying proportion unlike chemical with fixed valence both
antigens and antibodies are multivalent
 Antibodies are generally bivalent though IgM molecule may have five or ten combining site. Antigens
may have valance up to hundreds
Malaria vaccine
Malaria vaccine develops antibodies against the plasmodium falciparum, the most aggressive type of parasite
that causes malaria. The parasite has two main stages of development that take place into two different organs.

6. Eg: -
Steps: -
 First, migration of the parasite transmitted by the mosquito bite (sporozoite) to the liver
 Second, the sporozoite gets transformed inside the liver cell for generating hundreds of merozoites, which
then infect red blood cells
 Therefore, proteins at the surface of the parasite, ( sporozoites or merozoites) are constantly changing and
the ideal vaccine should be targeted through different proteins from the various stages to improve the
chance of obtaining protection or reducing the symptoms related mostly to the red blood cell infection
 Vaccine is one of few designed for targeting the two forms of the parasite ; sporozoites (infecting liver
cells) and merozoites ( infecting red blood cells) the vaccine uses virosomes as a delivery platform
What does a vaccine contain?
In addition to the bulk antigen that goes into a vaccine, vaccines are formulated (mixed) with other fluids (such
as water or saline), additives or preservatives, and sometimes adjuvants. Collectively, these ingredients are
known as the excepients. These ensure the quality and potency of the vaccine over its shelf-life. Vaccines are
always formulated so as to be both safe and immunogenic when injected into humans. Vaccines are usually
formulated as liquids, but may be freeze-dried (lyophilized) for reconstitution immediately prior to the time of
injection
Preservatives Vaccines
Phenol Typhoid Pneumococcal
Benzethonium chloride Anthrax
2-Phenoxyethanol Inactive Polio
Thimerosal Influenza
Adjuvant
ADJUVANT VACCINES
Aluminum salt Hepatitis A& B, Tetanus,
HemopylusInfluanza B
,Pneumococcal, Tetanus,
,diphtheria.
Aluminum salt and mono
Phospholipids Human Papilloma Virus
MF59 [oil in water emulsion] H1N1 influenza

7. General method for preparation of vaccines
1. The seed lot system
 the starting stage of preparation of all microbial vaccines is the isolation of suitable microbial strains
 microbial strain are mainly isolated from human infections and in some cases have required elaborate
manipulation and selection
 once a suitable strain is available a sizeable culture is prepared and distributed in large number of
ampoules and then stored at -7-degree or freeze dried. These culture is called “seed lot”.
 The seed is then used to make one or more atches of vaccine production
 If it is found satisfactory then it is tested for efficacy and safety in a clinical trials. Satisfactory result
in a clinical trials validate the seed lot and it is used for production of vaccines
Process of bacterial harvest
The harvest is a complex mixture of bacterial cell and metabolic product. The bacterial harvesting depend on the
nature of component that is required and, may involved one or more of the following procedure
 Killing
 Separation
 Fractionation
 Detoxification
 Adsorption
 Conjugation
Some examples
1. TAB vaccine (typhoid-paratyphoid A,B)
It is a sterile suspension of salmonella typhii and salmonella paratyphi A and B
TAB-C contain salmonella paratyphi C in addition to TAB
Preparation: -
o TAB vaccine is mixed polyvalent vaccine and is prepared by mixing of simple of vaccines of salmonella
typhii, s. paratyphi A and S, paratyphi B
o These strains are grow in acids digested agar medium and cultivated for 48ht at 37 degree
o Harvested with a sterile normal saline solution
o Strain are diluted to form 3000 million organism/ml of salmonella typhi and 2250 million organism/ml of
each salmonella paratyphi A and B
o Above strain are killed by adding 0.1% formalin or by heat treatment
o Bacterial strain are incubate at 37 degree for 4 days for detoxification and then tested for sterility
o Bacteril strain are mixed together to contain 1000 million organisms of S.typhi and 750 million organism
for each of S. typhi A abd B
o The suspension is transferred to final sterile containers and freeze dried
o The sterility and abnormal toxicity is evaluate further
Storage
o Store in a well closed container at temperature between 2-8 degree
Dose
o Prophylactic 0.5 ml (SC) 2-4 injection 2-4 week interval
o Booster dose give every 1-2 yr
Uses
o TAB also mixed with tetanus and cholera vaccine
o Prophylaxis of enteric infection
Quality contrl of vaccines
The quality control of vaccines is intended to provide assurance of safety and efficacy. They are checked in two
ways:
o In-process: in this quality control is the control exercised over starting material and intermediate. The
quality control of diphtheria and tetanus vaccine required that the product are tested for the presence of
free toxins
o Final product control: final product control is the quality control exercised by the monographs of a
pharmacopoeia of over product in their final container

8. o All vaccines are tested foe
 Identity test
 Potency test
 Safety test
 Sterility assay
 Free formalin test
 Abnormal toxicity testing
 Phenol concentration
 Presence of aluminum and calcium
3) Single shot vaccines
The single shot vaccine is a combination product of a prime component antigen with an
appropriate adjuvant and a microsphere component that encapsulates antigen and provides the
booster immunizations by delayed release of the antigen. To provide effective patient
protection, many traditional vaccines require multiple injections, which results in a costly and
inconvenient regimen. These disadvantages have spurred the development of single-shot
vaccines that can provide protection against infection with only one injection. Single dose
vaccines are given at a single contact point for preventing 4 to 6 disease, in order to increase the
therapeutic efficiency of such vaccines, adjutants are used
Manufacturing of single shot vaccines: -
Important factors in the manufacture of a microsphere based vaccine are high encapsulation efficiency and a
consistent particle production process. Several formulation parameter play an important role in obtaining a robust
process. Below we discuss the process and equipment used to manufacture several formulations
Several factors are critical parameter for the formulation of consist microsphere
 FIRST, the size distribution of the microsphere can be controlled by the shear a force applied during the
emulsification step in the bioreactor vessels. Factors that has been identified to influence this shear force
are the mechanical stirring speed in the bioreactor vessels the viscosity of PEG solution which is determine
by concentration and molecular weight of the PEG.
 SECOND, the presence of excipients in the starting composition can influence the matrix density and
encapsulation efficiency to the microsphere product either by direct effect on the microsphere formation or

9. on the protein characteristic. Finally polymerization condition such as KPS concentration, pH, and
temperature can influence the strength of the form hydro gel matrix
 Controlling particle size during process scale up
 The dextran microsphere preparation method describe by steinke’s et al., was initially perform on a 5-g
scale (containing 120 mg of microsphere) and used vortexing as a means to emulsify the dex-HEMA phase
in a continuous PEG phase . however vortexing is not practically at a large scale. Therefore we evaluate the
feasibility of stirring a process that is relatively scale-up as a means of emulsification ultimately at 500-g
scale
Delayed antigen release from dex-HEMA microspheres
 Once the freeze-dried microsphere product is rehydrated by reconstituting in an
aqueous solution, hydrolysis of the carbonate ester groups in the dex-HEMA will be
initiated
 This will increase the mesh size in the hydrogel network. The encapsulated protein
will be released when the mesh size exceeds the hydrodynamic diameter of the
protein
Future consideration for single dose vaccine delivery
 As most vaccines in the current immunization schedule are given as two or more discrete doses at
set time intervals, combining pulsatile delivery with the currently licensed vaccines formulations in
an attractive possibility.
 In this setting the existing vaccine in its soluble form constitutes the prime, and the encapsulated
forms acts as the boost.
 Single vaccinations that mimic multiple doses through pulsed release of antigen should be as
immunogenic as multiple dose regimes, providing that the polymer dose not alter the immune
response.
 The development of encapsulated vaccine technology with pulsatile release could offer a realistic
opportunity to replace existing repeated immunization vaccine and significantly improve
immunization.
Factors affecting antigen release
 Polymer nature
 Crystallinity
 Method of preparation
 Molecular weight of drug
 Carrier size and morphology
Adverse effects
 Fever
 Pain around injection site
 Muscle aches

10. Risk associated with vaccines
 The primary risk associated with vaccines, especially vaccines that utilize live organisms, is that the
vaccine itself causes illness.
 The vaccine may behave as a super antigen and over stimulate the immune system
 Some individual may have an allergic reaction to the vaccines
Recent trends
 Approaches for designing a preventive HIV vaccine
 Vaccine against dengue
 Malaria is mosquito born disease caused by a parasite. Recent studies showed that upon
encapsulating a subunit malarial antigen SPF66 in PLGA-mixture microspheres resulted in high
antibody levels in mice
Vaccine adjuvants: - adjuvants are the substances added to vaccines to help them work better. Adding an
adjuvant triggers the immune system to become more sensitive to the vaccine, the need for adjuvants are to
increase the therapeutic efficiency, they form depot of antigen at the site of inoculation with slow release of
antigens, it can improves the performance of vaccines by targeting the antigen to APC.
Types of adjuvants: - 1) gel type – aluminum hydroxide, calcium phosphate, 2) oil emulsion and emulsifier
based particulate based- liposomes, biodegradable microspheres.
Biodegradable polymers: - polymers comprised of monomers linked to one another through functional
groups and have unstable links in the backbone, broken down into biologically acceptable molecules that
are metabolized and removed from the body via normal metabolic pathways
Types of biodegradable polymers: -there are two types of biodegradable polymers. They are: natural
biodegradable polymers eg. Albumin, collagen, gelatin, etc . synthetic biodegradable polymers eg, aliphatic
poly(esters), polyanhydride, polyphosphazene, pseudo poly amino acid, poly( orthoesters), etc
Biodegradable polymers as adjuvants: -
 Biodegradable polymers such as poly(lactide-co-glycolic acids) is most commonly used for vaccine
delivery
 This polymers is mainly required for controlled release of the drug from polymer matrix
 Targeting to appropriate cell types to generate optimum response
 Development of formulation that can be used as non-invasive
4) Transdermal delivery of vaccines
o The skin is the largest and most accessible organ of the body. Vaccine administration to skin offer many
advantages include ease of access disease a potential for generation of both systemic and mucosal immune
response
o The skin is a site of vaccine delivery it approaches to overcome these barriers are cover included are
formulation approaches such as liposome such as electroportation, and technologies that creates micron
size pores in the skin

11. o The WHO estimate that 32% of hepatitis b virus infections, 40% of hepatitis c and 5% of HIV infection in
developing country are attributable to unsafe injection practice
o The development of needle free immunization method had thus become an important goal in global healt
care
o Dermal vaccination or transcutaneous immunization is a needle free method of vaccine delivery which has
the potential to reduce the risk of needle burn disease, access to vaccination by simplifying procedure
(trained personnel and use of sterile equipments not required) and assist in the implementation of multiple
boosting and multivalent vaccine regimes
o Skin as a site for vaccine delivery the skin has multiple barrier properties to minimize water loss from the
body and prevents the permeation of enviormental contaminants into the body
o These barriers can be considered as physical, enzymatic and immunological
o They range from formulation approaches such as liposomes to minimally invasive technology that
creates channel in the skin such as micro needle
o All method aim to overcome the stratum corneum barrier and target vaccines to immune responsive
cell such as langerhance cell
o Immunization by dermal route primary delivery method under investigation and development
a) liquid jet, b) epidermal powder immunization, c) topical application of vaccines to the epidermis
via
o Hair follicles
o Tap stripping to remove the stratum corneum
o Thermal or radio wave mediated ablation of the stratum cornea
o Colloidal carriers such as micro emulsion and liposomes increase dermal absorption
o Low frequency ultrasound as an adjuvant and to increase skin penetration
o Topically applied adjuvant to induce a potent immune responses
o Electroportation of the stratum corneum
o Shallow micro needles that penetrate into the epidermis

12. Skin as a site of vaccine delivery
The skin has multiple barrier properties to minimize water loss from the body and prevent the
permeation of environmental contaminants into the body; these barriers can be considered as- physical
barriers, enzymatic barriers, and immunological barriers.
Design and strategy for Transdermal vaccine delivery
 Liquid jet injections
 Energy based approaches
 Epidermal power immunization
 Colloidal carriers
Applications: -
o Application of liquid jet injector focused on delivery of macromolecules that do not passively
permeate the skin
o For administration of insulin and human growth hormone (HGH)
5) Mucosal delivery of vaccines
Mucosal surfaces area is major portal of entry for many human pathogens that are the cause of infectious disease
worldwide, immunization by mucosal routes may be more effective at inducing protective immunity against
mucosal pathogens at their sites of entry, efforts have focused on efficient delivery of vaccine antigens to mucosal
sites that facilitate uptake by local antigen-presenting cells to generate protective mucosal immune responses, the
adult human mucosa lines the surfaces of the digestive, respiratory and genitourinary tracts, covering an immense
surface area (400M2) that is 200 times greater than that of he skin, mucosal surfaces are typically categorized as
type-1 and type-2 mucosa, type-1 mucosa include surface of the lung and gut, where as type-2 mucosa include
surfaces of the mouth, esophagus and cornea.
Design and strategies for mucosal delivery: -
 Emulsion type delivery
 Melt in mouth strips
 Liposome based delivery
 Polymeric nano-particles
 Virosomes
Applications
 Natural entrance
 Systemic mucosal response
 Needle-free vaccination
 Easier production

13. Challenges solution (nanotechnology)
Enzymes protection
Barriers penetration targeting
Ag release sustained
Stimulation adjuvants
_____________________________________________ THE END _____________________________________________