INTRODUCTION:

The word vaccine is derived from Latine word variolae (cowpox). Which Edward Jenner demonstrated in 1798 could prevent smallpox in humans. A vaccine is a biological preparation that provides active immunity to a particular infectious disease. Vaccine Produced from living organisms, that enhance immunity against disease and either prevent (Prophylactic Vaccines) ,or in Some cases ,that disease (Therapeutic Vaccines). Vaccines are administered in liquid form, either by injection, by oral, or by intranasal routes.

Prophylactic vaccine is used to prevent the effects of a future infection by any nature or wild pathogen. (Ex- Anti-rabies vaccine) and the therapeutic vaccine is devised to harness the immune response to treat diseases ranging from cancer to multiple sclerosis. (Ex-Cancer vaccine).

Vaccination is the administration of a vaccine to help the immune system develop protection from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organisms.

Vaccination and immunization have a similar meaning in everyday language. This is distinct from inoculation, which uses unweakened live pathogens.

Types of vaccine:^3,4

1. Live-attenuated vaccine.

2. Inactivated vaccine

3. Recombinant sub-unit vaccine

4. Toxoid vaccine

5. Conjugate polysaccharide-protein vaccine etc.

Live attenuated vaccine:

Live attenuated vaccines contain whole bacteria or viruses that have been "weakened" (attenuated) to stimulate a protective immunity in healthy people but not disease. Most contemporary vaccines achieve this “weakening” by genetically altering the virus, either as a natural occurrence or as a mutation initiated purposefully by scientists. Some of our most powerful vaccines appear to induce a positive and long-lasting immune response. Example - MMR vaccine (measales, mumps, rubella vaccine), BCG vaccine against TB.

Inactivated Vaccine:

Vaccines that are inactivated are made up of whole bacteria or viruses that have been destroyed or changed to prevent them from multiplying. Except in patients with highly impaired immune systems, inactivated vaccines, which contain no live bacteria or viruses, cannot cause the diseases they protect against. Inactivated vaccinations, on the other hand, do not necessarily produce the same strong or long-lasting immune response as live attenuated vaccines. Examples- Hepatitis A, Influenza, Pneumococcal polysaccharide.

Recombinant sub-unit Vaccine:

Recombinant subunit vaccinations use an attenuated virus or bacterium to transfer microbial DNA to body cells. The carrier virus or bacterium is called a "vector," and the protein components that cause immune responses are synthetic peptides or antigens generated in eukaryotic or prokaryotic expression systems (e.g., E. coli, yeast) utilising recombinant protein expression technologies. The majority of vaccinations now on the market use pure recombinant protein or antigen complexes. Example- Hepatitis B vaccine, HIV vaccine etc

Toxoid Vaccine:

When bacteria invade the body, they release toxin (poisonous proteins), and it is the toxins, not the bacteria, that we want to be safe from. Toxoids are named for the fact that they resemble toxins but are not poisonous. They elicit a powerful immune response. Examples- DTP vaccine (Diphtheria, Tetanus, Pertussis vaccine.)

Conjugate Polysaccharide - protein vaccine:

The word 'conjugate' means 'joined' or 'related.' To get protection from a vaccine against certain bacteria, you must train your immune system to react to polysaccharides (complex sugars on bacteria's surface) rather than proteins. However, it was discovered early on that polysaccharide vaccines did not perform well in babies and young children.

Examples -Pneumococcal, meningococcal, Haemophlius influenzea type b (Hib) vaccine.

Definitions⁵

Vaccine:

A substance that activates a person's immune system to develop immunity to a particular disease, thereby shielding them from it. Vaccines are typically given as needle injections, but they may also be given by mouth or sprayed into the nose.

Vaccination:

Vaccination is the process of administering a vaccine to the body in order to confer immunity against a particular disease.

Immunity:

Immunity is the ability to resist an infectious disease. You will be exposed to a disease without being sick if you are resistant to it.

Immunization:

Immunization is a mechanism in which a person is vaccinated against a disease and thereby becomes immune to it. The terms vaccine and inoculation are often used interchange.

Vaccine administration routes^6,7

1. Oral route

2. Subcutaneous route

3. Intramuscular route

4. Intradermal route

5. Intranasal route

Oral Route:

Oral route safe and easy to administer and convenient for all ages. Vaccine are administered into the mouth without help of syringe or needle i.e known as oral vaccine.Example - Polio Vaccine.

Figure 1. Oral Route

Subcutaneous Route:

The vaccines is injected into the subcutaneous layer; above the muscles and under the skin. Needle at 45° angel. Example - MMR vaccine

Figure 2. Subcutaneous Route

Intramuscular Route:

The vaccine is injected into the muscle mass. Adjuvant-containing vaccines should be administered intramuscularly (IM) to minimise adverse local effects. Example - Hepatitis B vaccine.

Figure 3. Intramuscular Route

Intradermal Route:

Vaccine that can be provided this route. BCG vaccine administered intradermally decreases the risk of neurovascular damage. Due to the small size of newborns’ arms, health workers believe BCG is the most difficult vaccine to administer. The BCG vaccine needs a small, narrow needle (15mm, 26 gauge).

Figure 4. Intradermal Route

Intranasal Route:

Nasal vaccine delivery acts as a "first entry block," avoiding pathogen entry when invading the mucosal surface and inducing local microbial-specific immune responses, increasing the vaccine's safety and efficacy. Examples-Intranasal flu vaccine

Figure5. Intranasal Route

Steps involved in vaccine production -⁸

1. Selecting the strains for vaccine production.

2. Growing the Microorganisms

3. Isolation and Purification of microorganisms

4. Inactivation of organism

5. Formulation of vaccine

6. Quality control

Selecting the strains for vaccine production:

The seed:

Small amounts of a specific virus are used to start the manufacturing process (or seed). Viruses or bacteria used in manufacture shall be derived from a seed lot system. A record of the origin, passage history and storage conditions should be maintained for each seed lot. The virus must be free of impurities. The seed must be kept in ‘ideal’ conditions, usually frozen that prevent the virus from becoming either stronger or weaker than desired. Stored in small glass or plastic containers.

Selecting the strain:

The choice of the seed is depend on a number of factors including the efficacy of the efficacy of the resulting vaccine, and its secondary effects.

If possible, the bacterial stain or cell line should be obtained from a recognized culture collection with an established and documented provenance.

Alternatively, if the chosen vaccine stain is an ‘in house’ clinical isolate, it will be necessary to compile a complete history of the stain, including details of its isolation, Identification, and maintenance for product registration.

Growing the Microorganisms (Virus):

After defrosting and warming the seed virus under carefully specified conditions (i.e., at room temperature or in a water bath), the small amount of virus cells is placed into a "cell factory," a small machine that, with the addition of an appropriate medium, allows the virus cells to multiply. Each type of virus grows best in a medium specific to it, established in pre-manufacturing laboratory procedures, but all contain proteins from mammals in one form or another, such as purified protein from cow blood. The medium also contains other proteins and organic compounds that encourage the reproduction of the virus cells. As far as the virus is concerned, the medium in a cell factory is a host for reproduction. Mixed with the appropriate medium, at appropriate temperature, and with a predetermined amount of time, viruses will multiply.

Isolation and Purification of microorganism:

Product isolation:

It is the removal of those components whose properties very markedly from that of the desired product.

Purification:

Purification selectively seperates and retains the desired product at the highest purity per it's pre- determined specification. (Remove unwanted compounds)

The most common methods of vaccine production:

1. Centrifugation

2. Filtration

3. Chromatography

Inactivation of microorganism:

Killed or inactivated vaccine:

Viruses can be lipid coated (enveloped) or non enveloped.

Viruses inactivation involves dismantling a viruses ability to infect cells without actually eliminating the virus.

Machanism:

1. By attracting the viral envelope or capsid and destroying it's ability to infect or interact with cells.

2. By disrupting the viral DNA or RNA and preventing replication.

a) Solvent / detergent (S/D) inactivation

b) Acidic pH inactivation (low pH treatment)

c) UV inactivation

Formulation of Vaccine:

1) Suspending Fluid:

1. Sterile water, saline or fluid containing protein.

2. Egg Protein - Which are prepared using chicken eggs (influenza and yellow fever vaccine)

3. Yeast protein - Hipatitis B vaccine

2) Preservatives and Stabilizers-

1. Aluminium, Phenol, Glycine

2. Monosodium glutamate (MSG) And 2- phenoxy ethanol used as stabilizers

3. Antibiotics- (neomycin, streptomycin, Polymaxin B, amphotericin B.

4. Thimerosal- Mercury- containing preservatives. Used as DTPs vaccine, Hepatitis B and Hemophilus influenza type B

3) Inactivating Agents:

1. Formaldehyde - mostly used toxoid vaccines (eg. influenza Vaccines which have been determined to be safe and effective move on to phase III tests, which focus on the vaccine's efficacy in hundreds to thousands of volunteers. This step can take several years to complete, and it allows researchers to compare vaccinated volunteers against those who have not been vaccinated in order to identify any actual vaccination reactions.

2. If a vaccine passes all of the testing phases, the manufacturer can submit an virus, polio virus and diphtheria and tetanus toxins.)

3. Beta propiolactone- (eg.Rabies virus)

4. Glutaraldehyde- (eg.acellular pertussis vaccine)

4) Adjuvants or enhancers:

Aluminium gels or salts (Alum)

Alum is used in several vaccines eg. DTP Vaccine, Hepatitis A, Himophilus influenza B (Hib).

Quality Control:

To protect both the purity of the vaccine and the safety of the workers who make and package the vaccine, conditions of laboratory cleanliness are observed throughout the procedure. All transfers of virus and media are conducted under sterile conditions, and all instruments used are sterilized in an autoclave (a machine that kills organisms by heat, and which may be as small as a jewel box or as large as an elevator) before and after use. Workers performing the procedures wear protective clothing which includes disposable tyvek gowns, gloves, booties, hair nets, and face masks. The manufacturing rooms themselves are specially air conditioned so that there is a minimal number of particles in the air.

Preclinical Trials^9,10

Preclinical trials are laboratory tests of a new medicine or medical device, usually performed on animals, to see if the hoped-for treatment works and is safe to test on humans. The new drug are first tested in laboratory animals before moving to phase l trails. Example - Polio vaccine-Firstly tested for adverse effects and immunogenicity in monkeys as well as non- primates and lab mice.

Phase l:

The Phase I study involves introducing the vaccine candidate to healthy people in order to determine its safety. A Phase I vaccination study consists of healthy volunteers who are given either the candidate vaccine or a "control" treatment, such as a placebo or an adjuvant-containing cocktail, or a proven vaccine (which might be intended to protect against a different pathogen). The main goal is to look for a signs of safety and evidence of a immunological response.

Phase ll:

The immunogenicity and toxicity results from Phase I in a small group of healthy volunteers are used to transfer to Phase II. More healthy volunteers from the vaccine target demographic (hundreds of people) will be used in Phase II to determine reactions in a larger group of people and try alternate schedules.

Phase lll:

Phase III trials continue to monitor toxicity, immunogenicity, and SAEs. Before being approved for general production, the vaccine must be shown to be safe and efficacious under natural disease circumstances. The Food and Drug Administration (FDA) in the United States is in charge of vaccine approval.

Phase Lv:

After a vaccine has been approved and promoted, phase IV trials are used to collect data on vaccine usage, side effects, and long-term immunity. Phase IV trials may show harmful effects, such as an increased risk of liver failure or heart attacks, which may result in a drug being removed from the market or restricted to specific uses.

Challenges of vaccines production:¹¹

Priorities for overcoming the outstanding issues and barriers in successful vaccine development:

1) Problem:

Inadequate preclinical data and lack of detailed information on protective correlates of immunity contribute to product failure in clinical trials.

Action required:

Development of more relevant animal models; more human samples to be collected and analysed; increased use of experimental human challenge infections.

2) Problem:

Lack of information on the infectious exposures of intended vaccine recipients.

Action required:

More human samples to be collected and analysed.

3) Problem:

Vaccines are to be used in populations with less-responsive immune systems.

Action required:

Gain a greater understanding of the mechanisms of action of currently used adjuvants; development of vaccine delivery systems specifically for use in immunocompromised populations.

4) Problem:

Antigenic variation requires constant updating of vaccine formulations.

Action required:

Seek conserved antigens; monitor genetic variation of infectious organisms in the community.

5) Problem:

High costs of vaccine development result in premature abandonment of potentially useful products.

Action required:

More investment in vaccine research.

6) Problem:

Inadequate access to vaccines in poorer countries, especially those for use against tropical diseases.

Action required:

More tiered pricing strategies; facilitate the development of vaccines in developing countries.

Opportunities:¹²

A variety of careers are available in basic vaccine research and development, clinical trials, production, and distribution of vaccines to the public. These jobs are available in universities, industry, government laboratories and agencies, hospitals, and on the front line of vaccine distribution all over the world.

Typically, most people start their career in vaccines with an undergraduate degree such as a Bachelor of Science (BS) in fields such as cellular or molecular biology, chemistry, biochemistry, or microbiology. It is helpful, before earning these degrees, to have had a combined strong background in high school science classes and a natural sense of curiosity. Many vaccine development jobs require masters and/or doctorate degrees (MS and/or PhD) that require several years of additional study beyond the BS degree.

CONCLUSION:

Vaccine are one of the most effective health interventions ever developed. Vaccine industry has been proved to one of the fastest growing sector of the past decade and is forecasted to do so in future also. Three types of vaccine are currently used in humans; attenuated, inactivated and recombinant vaccine. Adjuvants are also used to association with vaccines for increasing the immune response. As the vaccines have a lot of benefits, they do carry some harmful effects too.

REFERENCES:

1. Basic Concepts of Vaccination.pdf; Vaccine fact book 2012.

2. Vaccine. Wikipedia

3. S. Satyalakshmi; Biotechnology sem Vl, B. Pharmacy Council of India, New Delhi; PV book ,Pg no.257

4. https://www.nature.com/articles/nbt1261

5. https://www.cdc.gov/vaccines/ immunization basic/ cdc

6. JippyJack; Vaccination, History, Programmes Published in Education, Technology, Health and Medicine on Feb1,2016

7. Vaccination wikipidia

8. Vijaya Choudhury; Slide Presentation Apr.18,2012; Published in Education, Technology, Health and Medicine

9. Vaccine Trial. Wikipidia

10. Jaipur National University Jaipur, Published in Health and Medicine in Feb 11 ,2013(www.slideshare.com)

11. Petra Oyston and and Karen Robinson; Journal of Medical Microbiology (2012),61,889-894.

12. hettps;//scholar.google.com/opportunities challenges for vaccine production

Received on 27.08.2021 Modified on 23.09.2021

Asian J. Res. Pharm. Sci. 2022; 12(1):83-87.

DOI: 10.52711/2231-5659.2022.00014