Dhristi NEET 2022-24

About Vaccine

A vaccine is a substance that is used for the production of antidotes in the body and provides immunity against one or a few diseases. In biological terms, a vaccine is defined as a biological and formulated preparation to provide acquired immunity for a particular disease. 

Generally, a vaccine is an agent which contains a weakened or killed form of the disease-causing agent, its surface, or its toxins. When this solution is introduced to the human body, the immune system is able to identify the threat and destroy it. More than this, the human body will recognize the threat and can initiate an appropriate response in the future also.


The process of implementing the vaccine is called vaccination. It is responsible for the clearance of many diseases, especially infectious diseases like smallpox and chickenpox. The word "vaccine" is derived from the Latin word "vaccines" which means "from the cows".

Invention of Vaccine

The practice of immunization of the body dates back hundreds of years, but the first official vaccination was developed by Edward Jenner who is considered the founder of vaccinology. In 1796, he injected a 13 year-old-boy with cowpox(vaccinia virus) and established immunity to smallpox. In 1798, the very first smallpox was developed. During the 18th and 19th centuries, systematic implementation of mass smallpox immunization culminated in its global establishment in 1979.

Types of Vaccines

There are many initiations to vaccine development, but vaccines can be mainly classified by how the antigen, active component, that produces a specific immune response against the disease-causing organism, are prepared.

Classification of Vaccines

  1. Live Attenuated Vaccines:

Attenuated vaccines are developed in many several ways. The common methods include passing the disease-causing virus through a series of cell cultures or animal embryos. When the vaccine virus is implemented in a human, it will be unable to replicate enough to cause illness, but still promotes an immune response that can protect against future infection.

  1. Inactivated Vaccine:

Vaccines of this category are developed by inactivating a pathogen, typically using chemicals or even heat such as formaldehyde or formalin. This destroys the pathogen's ability to replicate but keeps it intact so that the immune still remembers it.

  1. Toxoid Vaccine:

There are some bacterial diseases that are not directly caused by a bacteria itself, but by producing toxins by the bacterium. For this type, immunization of pathogens can be developed by inactivating the toxin that causes disease symptoms. As the viruses or organisms used to kill or inactivate vaccines, this can be done through treatment with a chemical such as formalin or by heat.

  1. Subunit Vaccine:

Subunit vaccines are only used as part of a target pathogen to promote a response from the immune system. This can be done by isolating a specific protein from a pathogen and presenting it as an antigen on its own.

  1. Conjugate Vaccine:

Conjugate vaccines are somehow similar to recombinant vaccines, they are made up of a combination of two different components. Conjugate vaccines, however, are made up of using the pieces from the coat of bacteria. These coats are chemically linked to a carrier immune protein, and this is how a combinational vaccine is used.

  1. Valence Vaccine:

Vaccines may be monovalent. The monovalent vaccine is designed to be immune against a single microorganism or single antigen. A multivalent or polyvalent vaccine is made to immunize against two or more viruses of the same microorganism.

  1. Heterotypic Vaccine:

Heterologous vaccines are also called "jennerian vaccines". These vaccines are pathogens of different animals that either do not cause disease or cause disease or cause mild disease in the organism being treated.

  1. mRNA Vaccine: 

An mRNA Vaccine (or RNA Vaccine) is a different type of vaccine which is a combination of nucleic acid RNA, packaged within a vector such as lipid nanoparticles. 


Vaccination is a process involving introducing deactivated/ weakened disease-causing microbes into a person, or a vaccine is administered to a person to generate immunity from that disease. Vaccination is generally injected or administered orally. It is the drug (weak pathogen/ inactivated) that is administered to a person to prevent the onset of a disease.

Uses of Vaccination

Vaccines are very important because they protect us from infectious diseases. In some areas or populations, infectious diseases are endemic. For example, cholera, polio, smallpox, hepatitis B and so on. To fight against these diseases, we need vaccines to boost our immune systems and prevent harm.

What is an Immunization?

It is the ability of the human body to produce an immune response either naturally, or through vaccines. These approaches develop immunity or resistance to a specific illness. Immunization can be defined as the process by which a person is made to fight against a particular disease by the administration of a vaccine. The basic principle of immunization is that the human body starts to produce antibodies against disease through vaccines so that the person is safe from the infectious disease. The body repeats the process of development of infectious agents and memory cells that can develop antibodies immediately upon further exposure to the infectious agent.

Process of Immunization

  • The process begins when a person is injected through the vaccine and then their bodies begin to develop immunity to fight against the disease.

  • The body generates immunity through this vaccine for the disease rabies.

  • This method has proven to be very effective to prevent a number of infectious diseases.

  • Smallpox, Tetanus, measles, and other diseases have vaccines.

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FAQs (Frequently Asked Questions)

What is a Vaccine?

A vaccine can be defined as a substance that is used to boost the production of antibiotics, which provides immunity against diseases.

 A vaccination is a live, inactivated microbe or virus that is injected into the body to imitate an illness. The injected germs do not make a person sick since they are 'dead.' Vaccines, on the other hand, encourage the body's immunological response to combat the disease. A vaccination is a substance that boosts immunity to a specific illness. It is a biologically manufactured product that contains typical agents that resemble a disease-causing pathogen, generated from weakened or dead microorganisms, one of their surface proteins, or their toxins. It aids in the activation of the immune system as well as the identification and destruction of invasive bacteria as foreign agents, allowing the immune system to recognise and eliminate any germ met afterwards. The distinctions between vaccinations, vaccines, and immunizations must be understood. Let's take a look at each one separately. A vaccine is an antigenic material that produces immunity against a disease and is administered by needle injections, oral administration, or aerosol delivery.

Name the Types of the Vaccine?

There are generally 8 types of vaccines developed to date, which include:

  • Inactivated vaccine

  • Attenuated vaccine

  • Toxoid vaccine

  • Subunit vaccine

  • Conjugate vaccine

  • Valence vaccine

  • Heterotypic vaccine

  • mRNA vaccine 

How do Vaccines work?

Although no treatment can be said to be flawless, most vaccinations provide protection in 90-100 percent of instances. Better sanitation and hygiene can certainly assist to limit the spread of illnesses, but the microorganisms that cause them still exist. As long as germs persist, they will continue to make people sick. Before a vaccine may be used in the United States, it must first be approved by the Food and Drug Administration, or FDA. Before the FDA approves a vaccine, it must undergo comprehensive testing to ensure that it is safe. Clinical studies, for example, compare groups of people who get a control, such as a placebo, against groups of people who receive a vaccination. Only after the FDA certifies that a vaccine is safe for its intended application is it licensed. When you look at a history of diseases that may be prevented with a vaccination, you'll see that after a vaccine is approved, the number of instances starts to decline. Every year, vaccines save millions of lives. When a segment of a city or town is vaccinated against a communicable illness, it protects multiple people of the same community against the disease, reducing the risk of an epidemic.

How does the immune system work?

We need to learn more about how our immune system functions in order to better comprehend vaccinations. White blood cells are unique cells found in human circulation. They play a critical role in defending against foreign invaders such as viruses and bacteria. Antigens are the invaders in issue. White blood cells serve as our body's armed forces. They're always on the lookout for antigens that have made their way into our bodies and are endangering our health.

Antibodies are a type of protective protein that circulates in our blood. They remain dormant until they are activated by an immunological response, such as the recognition of an antigen.

The microbes have no chance now that this massive army of antibodies has joined the battle with the white blood cells. Consider the case of an influenza virus that has entered your body and began multiplying. These antigens have been detected by the white blood cells that patrol your circulation. They assemble their forces, generate a few billion antibodies specifically designed to combat this virus, and unleash a major attack. The body will take some time to thoroughly fight off these viruses, which is why you are experiencing symptoms of disease for a short period. If you have a healthy and strong immune system, though, you will be back to normal in a few days. The good news is that your body has built up a strong army of antibodies against that infection. They're still looking for the same antigen to infiltrate. It will be so quickly overrun by the immune reaction the next time it enters your body that you will not even notice any symptoms.