INTRODUCTION
The purpose of vaccination is to protect individuals against diseases caused by bacteria, viruses, and microorganisms. It also aims to prevent transmitting or spreading of infection in the community.Vaccines play an indispensable role in keeping us well. Even now (2020), the World eagerly awaits for the vaccine for the pandemic disease Covid19.
In the present century, vaccination process begins as soon as the baby borne and it continues for many years for various types of infections.
WHAT IS VACCINE AND VACCINATION?
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Vaccine: A vaccine is a biological preparation (substance) that injected into the body to prevent or control the diseases or infections caused by pathogens (bacteria, viruses, or any other organisms). It prepares the body to fight against the diseases faster and effectively.
According to theoretical science, a vaccine infuses antigens (toxins such as bacteria, viruses, or disease causing microorganisms) into the body. In the future, these antigens create antibodies (disease fighting proteins) to fight against pathogens. In other words, these antigens stimulate and train the immune system to fight against the pathogens in the future since the immune system cells have memory.
A vaccine can be prophylactic or therapeutic. A vaccine can be oral (given in mouth), injection (through the needle) or sprayed into the nose. An injection is the most used method.
Vaccination : The administration or treatment with the vaccines to produce immunity to fight against the pathogens/disease is called vaccination.
The words vaccine and vaccination originated from Variolae vaccinae. This word minted by Edward Jenner to denote cowpox.
WHAT IS IMMUNIZATION?
Immunization is the method whereby a person gained immune or resistant to a contagious disease, typically by the administration of a vaccine. Vaccines incite the body’s own immune system to guard the person toward succeeding in contamination or disease. Immunizations also called vaccinations, needles, shots or jabs.
Once the vaccination is given, the immune system identifies the vaccine agents as foreign and destroys them, and recalls them. If the pathogen confronted, the body’s immune system identifies the protein coat of the pathogen and prepares itself to respond.
Firstly, it neutralizes the target agent before it enters the human cells and then it identifies the infected cells and destroys them before it multiplies or replicates.
VACCINE INGREDIENTS
A vaccine composed of ingredients, which serves for specific purposes like
i) Boosts immunity (To fight against the diseases)
ii) To keep the vaccine safe
iii) Used during the production
BOOSTING IMMUNITY
When a vaccine infused into the human body, the ingredients present in the vaccine reacts, develops the immunity power for that particular disease, and helps the immune system to fight against the diseases.
ANTIGENS : these are weak or dead pathogens that causes diseases. It is present small amount in the vaccine. This teaches the immune system how to respond or fight against that disease faster and effectively.
ADJUVANTS : Some vaccines contain one or more adjuvants. Adjuvants boost the immune system to respond very strongly to the vaccine and thus it increases the immunity to fight against the disease. Aluminium salts or gels added as Adjuvants.
TO KEEP THE VACCINE SAFE
Some ingredients present in the vaccines keep the vaccine safe for a long period as they were prepared and protecting it from getting affected by outside germs or bacteria.
Vaccines contain some preservatives to deter the contamination of bacteria or fungus. Thimerosal (in U.S. and Japan) or Thiomersal is one of the preservatives.
Thiomersal is mercury-containing antimicrobial added to the vaccine to prevent the contamination and growth of bacteria in the vaccine. Thiomersal is now added only in the multi-use influenza vaccine at a reduced level i.e., a single dose contains less than 1micro gram of mercury.
Stabilizers :
Monosodium glutamate (MSG) and 2-phenoxyethanol used as stabilizers protect
the vaccine unchanged when it is exposed to heat, light, acidity, or humidity.
DURING THE PRODUCTION
The ingredients, which used while developing the vaccine, removed after the developing process but a tiny amount of substances left over the final product, which is not harmful. Examples of substances used during developing vaccines include :
Cell culture (growth) material : like eggs, used to grow vaccine antigens.
Deactivating ingredients : Formaldehyde used to weaken or kill viruses, bacteria or toxins in the vaccine. It kills bacteria that contaminate the vaccine during production.
Antibiotics : Neomycin, protects the vaccine from outside germs or bacteria. It helps to stop outside germs and bacteria from growing in the vaccine. It prevents the growth of bacteria during the production and storage of the vaccine.
TYPES OF VACCINES
There are numerous different types of vaccines are present to cure many diseases. Each type of vaccines coded to incite the immune system to fight against the pathogens/germs.
While developing the vaccines the Scientists ponders about
i) How the immune system reacts to the pathogen?
ii) Who requires to be immunized against the pathogen?
iii) The most reliable technology to formulate the vaccine.
Based on these factors the scientists develop vaccines.
There are four main types of vaccines:
- Live-attenuated vaccines
- Inactivated vaccines
- Subunit, recombinant, polysaccharide, and conjugate vaccines
- Toxoid vaccines
LIVE-ATTENUATED VACCINES
Live vaccines use a weekend form of germ, which induces the disease. This vaccine progressed in several ways. The prevailing method used to produce this vaccine involves the transmission of disease-causing germs through a series of cell cultures or animal embryos especially chick embryos.
In each series of transmission, the germ grows and replicates in embryos but loses its ability to replicate in human cells. Nearly or more than 200 various embryos or cell cultures used to find the targeted virus for preparing the vaccine. When the germs become unable to replicate in human cells, it is the time to use for the vaccine.
When this vaccine is given to, the patients (human) the germs will not be able to replicate but it stimulates the immune system to fight against the germs when attacked in the future.
Most of the Live-attenuated vaccines are viral and a few are bacterial in nature. Examples of these vaccines used to protect the diseases are :
- Measles, Mumps, Rubella (MMR combined vaccine)
- Varicella (chickenpox)
- Influenza (nasal spray)
- Rotavirus
- Smallpox
- Yellow fever
This vaccine has some limitations/disadvantages. Since this vaccine contains some weakened live virus, people with less immunity, long-term health problems, who have undergone organ transplant, should consult their Physician before injecting. In rare cases, this vaccine may replicate or mutate and cause diseases.
INACTIVATED VACCINES
Vaccines of this type created using inactivating the pathogens. The virulent germs inactivated using heat, radiation or chemicals such as formaldehyde or formalin. This destroys pathogen's ability to mutate or replicate. In this type of vaccines, the viruses are not alive but still, the immune system recognizes it.
Inactivated vaccines are not much strong as Live-attenuated vaccines. Inactivated vaccines give short-term protection so it is given in several doses to boost immunity.
Some of the inactivated vaccines are :
- Hepatitis A
- Flu
- Polio
- Rabies
SUBUNIT, RECOMBINANT, POLYSACCHARIDE, AND CONJUGATE VACCINES
These vaccines use only the part, fragment, or specific pieces of germs. The part can be protein, sugar, or capsid of the pathogen. Subunit vaccine developed by separating the protein part of the pathogen and making it as an antigen.
One method of developing this vaccine is via Genetic Engineering. A protein made up of gene coding infused into another virus, pathogens, or into producer cells in culture. During this process, the virus or pathogen reproduces or the producer cells metabolize and creates a vaccine protein. The result of this method is a recombinant vaccine. The immune system identifies this protein and in the future it defence against that virus. Hepatitis B vaccine made using the recombinant method.
The second method in developing vaccines through genetic engineering is in each strain of the virus a single viral protein is separated. In this protein, a virus like particle (VLP) created and this particle does not contain genetic material of that virus from which the strains are taken. Since there is no genetic material it does not causes illness and boosts immunity in the future for protection. The Human papillomavirus (HPV) vaccine made using this method, composed of viral major capsid protein.
Conjugate vaccines are developed or created using two different components. Certain bacteria have polysaccharide outer coats, which are less in immunity. This vaccine prepared from the fragments of these outer coats of the bacteria. These outer coats chemically linked to proteins and thus the vaccine made. Conjugate vaccines are more powerful since the piece of outer coats of bacteria does not stimulate strong immunity but the carrier (linked) protein does and fights against the pathogens when infected in the future.
These vaccines used for all people whoever needs, people with low immunity power, a prolonged health problems can use this vaccine if required. Like inactivates vaccines, these vaccines injected in several doses to boost immunity and to protect against the diseases. These vaccines used to safeguard against :
- Human papillomavirus (HPV)
- Hib (Haemophilus influenza type B)
- Hepatitis B
- Whooping Cough
- Pneumococcal disease
- Meningococcal disease
- Shingles
TOXOID VACCINES
Toxoid vaccines are prepared from the harmful product (toxin) of the pathogen, which causes the disease. Immunizations created using inactivated toxins called Toxoid. To boost the immune system for this type of germs is by deactivating the toxin, which responsible for the disease. The toxin deactivated using the chemical formalin, by heating or some other methods.
These vaccines injected in several doses to boost immunity and to protect against the diseases.
Toxoid vaccines used to defence against:
- Diphtheria
- Tetanus
EXPERIMENTAL STAGE
Apart from the above types, numbers of innovative vaccines are in the development stage and in use. Few are:
Dendritic cell vaccines : developed using dendritic cells with antigens. These types of vaccines have some positive preliminary results for treating brain tumours.
DNA Vaccination : the mechanism used here is injecting viral or bacterial DNA into human or animal cells. One advantage of DNA vaccines is that they are very easy to produce and store.
Recombinant vector : Produced by combining the physiology of one microorganism and the DNA of another. Example: RVSV-ZEBOV vaccine used in 2018 for the Ebola virus in Congo.
RNA vaccine : It is a novel type of vaccine, composed of the nucleic acid RNA. A number of RNA vaccines are under development to fight against the disease COVID 19 virus.
T-cell Receptor : These vaccines are in the developmental stage for several diseases.
DEVELOPMENT STAGES
The development of vaccine is long and complex process. It takes more than 10 -15 years. It costs nearly $500 Million. The developmental stages are :
Exploratory or Discovery : This stage takes 2 – 5Years. Basic laboratory research made. Scientists identify the antigens to prevent or treat the disease. The antigens could be viral like particles, bacteria, or any other substances from the pathogens.
Pre – Clinical : Pre-clinical studies use tissue-culture or cell-culture systems and animal testing. Animal includes mice and monkeys. This stage lasts for 2 years.
Clinical Development
Phase I : In this stage the safety of humans and the immunity response determined. The vaccine tested on humans involving a small group of adults (20 – 80 peoples). If the vaccine developed for children, the researchers first will make a test on adults and then they gradually decrease the age until they reach the target age.
Phase II : In this stage, many or several hundred individuals are been tested. In this stage, the researchers study about the humans safety on vaccine, immunity, doses, schedule of immunization. It lasts for 2 - 3 years.
Phase III : In this stage, more people are involved. 1000 – 10000 people are tested. In this, the vaccine safety in a large groups of people identified. In certain cases, the side effects will not be shown in earlier stages since it involved a fewer number of peoples. Therefore, in this stage, the vaccine tested on many numbers of peoples to identify
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· Does the vaccine stop the disease?
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· Does it inhibit contagion with the germs?
- Will it build the antibodies?
- How does the immune system respond to the pathogen?
It takes 2 – 4 years.
Phase IV : This is optional. The pharmaceutical industry or manufacturer may continue to test the vaccine after the release for the safety purposes.
Manufacturing and Delivery
Manufacturing a vaccine is highly expensive and it requires specialist facilities. Around or more than, 1000 doses are required for the Phase III stage.
According to the Wellcome Trust a U.K research charity, “The discovery and research phase is normally two-to-five years. In total, a vaccine would take more than 10 years to develop fully and costs up to $500 million”.
ANTI-VACCINE
The richer countries have the poor opinion on vaccines. They believe vaccines are not safe. The Wellcome Trust a U.K research charity surveyed more than 140,000 people in more than 140 countries about their views on science and health. 79% (8 in 10) of people said vaccines are safe.
The survey says people in Western Europe have the lowest confidence in vaccines. France is strong against vaccines or vaccination.
On the flip, In Bangladesh, 98% says inoculations are safe and effective followed by Rwanda with 97%.
CONCLUSION
"Vaccination is one of the world’s most successful health interventions, saving as many as 3 million lives every year. Vaccination is among the most important developments in human health, saving millions of lives a year", says WHO.
So far, only Smallpox declared officially eradicated by vaccination. By last year (2019), one of the two last surviving strains of Polio eradicated.
ALSO READ : THE DISCOVERY OF VACCINATION
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