From childhood, you have heard that prevention is better than cure. It is a fact to follow in real life. In the world of medicine that relates to science and biology, prevention is always better. The reason is that sometimes when we fail to prevent any disease by not preparing in advance, the cure may be unavailable or hard to get. Therefore, it is always wise to avoid certain conditions by planning. Prevention helps when you are in close contact with a person suffering from an infectious or contagious disease. In this section, we will talk about Immunization and vaccination as ways to prevent infections.

Diseases are conditions that impair the smooth and efficient working of our body and mind. When we go out for treatment in case of an infection, it is possible that we face some obstacles. The difficulty can be a disease that has completely damaged the body functions beyond recovery, or a person suffering from an ailment is confined to bed as there is no cure or a person suffering from infection is likely to spread the sickness to others as well. In such situations, it is necessary to have some preventive measures in place.

Vaccines and immunization are considered as one of the most successful ways of prevention when it comes to taking care of one’s body. These are biologically prepared tools that reduce the risk of human beings contracting diseases, some of which can be life-threatening. Vaccines are usually administered through injections. They make us immune by working with the natural defenses present in our bodies.

Another aim of more and more vaccines being administered is to prevent and control outbreaks of infectious diseases. Hence, it is believed that immunization is a crucial key component of primary health care. According to the World Health Organization (WHO), immunization and vaccines help prevent around 2-3 million deaths each year from severe diseases like tetanus, diphtheria, pertussis, measles, and influenza.

Types of Immunization

Immunization is a process through which a person who is immunized develops resistance to particular diseases. This resistance is developed by administering a vaccine. A vaccine is a dose of specialized medication that stimulates the immune system of a person and helps beat certain diseases. The process of immunization has proved advantageous in preventing many infectious diseases. It has also contributed to a decrease in the mortality rate. Immunization is done through vaccines. Today, vaccines are available against smallpox, measles, tetanus, polio, etc.

Immunization and vaccines are administered to adults and infants through public health programs. In the case of infants, the pediatrician administers regular vaccinations that are set in a schedule.

Types of Vaccines

There are different types of vaccines. Each type serves a definite purpose. The design of each vaccine is that it teaches your immune system how to fight certain kinds of germs and the dangerous diseases they cause. Vaccines are prepared after lots of research in the laboratory. When scientists create a vaccine, they consider the following aspects:

How does the immune system respond to the germ?
Who requires vaccination against the germ?
The best technology to create the vaccine

Depending on these factors, a scientist decides the type of vaccine they need to develop. There are four main types of vaccines-

Live - Attenuated Vaccine – they use a weakened form of the germ that causes disease. These vaccines are similar to the natural infection that they prevent. They create a secure and long-lasting immune response. 1 or 2 doses of live vaccines are enough to give lifetime protection against a germ and the disease they cause. Examples are smallpox, chickenpox, yellow fever, rubella, and measles.
Inactivated vaccines use the killed or dead version of the germ that causes a disease. Inactivated vaccines typically do not provide immunity or protection as strong as live vaccines. One may need several doses or boosters shots over time so that the resistance stays against the diseases. Examples are Hepatitis A, Flu, Polio, and Rabies.
Polysaccharide, subunit and conjugate vaccines use specific parts of the germ like its protein, sugar, or capsid (casing or covering around the germ). As these vaccines use particular pieces of the germ, they give a powerful immune response that targets vital parts of the virus. One may need booster shots to keep the immunity steady. Examples are Hepatitis B, HPV, Whooping cough, Pneumococcal disease, and Shingles.
Toxoid vaccine uses a toxin or harmful product made by the germ that causes a disease. These vaccines create immunity against those parts of the germ that cause disease instead of the whole germ itself. It means that the protection or immune response is targeted at the toxin rather than the germ. One may need booster shots to get ongoing protection against diseases. Examples are Diphtheria and Tetanus.

Types of Ingredients in Vaccines

Vaccines differ depending upon the ingredients that are combined to prepare them. Each of the ingredients used to prepare a vaccine serves a different and specific purpose:

Provide protection or immunity to the body
Keep the vaccine safe, effective, and long-lasting
Providing material for the production of the vaccine and more

The various types of ingredients used to produce vaccines include:

Preservatives to prevent contamination
Adjuvants to help boost our bodies’ response to the vaccine
Stabilizers that help keep the vaccines effective post their manufacture
Residual cell culture materials that help grow enough of the bacteria or virus needed to make the vaccine
Residual inactivating ingredients to help kill inactivated toxins or kill viruses during the manufacturing process.

Infant Immunizations

Strong immunity or protection is a way to prevent diseases. This statement is especially applicable to newborns or small babies, who are yet to get the benefits of a grown-up’s immunity and preventive coping mechanisms against infections. When a baby is born, his or her immune system is not fully developed. It can put a child at a higher risk for infections. Administering vaccines and supplying immunization reduces the risk of infection by working with the natural defense to help develop protection, resistance, and immunity to diseases.

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FAQs on Vaccination and Immunisation in Human Health and Disease Prevention

1. What is vaccination and immunisation?

Vaccination is the administration of a vaccine to stimulate immunity, while immunisation is the process by which a person becomes protected against a disease. Vaccination involves introducing a weakened or inactivated pathogen (or its antigen) into the body. Immunisation is the result of this process, where the immune system develops protection through the production of antibodies and memory cells. Thus, vaccination is the action, and immunisation is the outcome.

2. How do vaccines work in the immune system?

Vaccines work by stimulating the immune system to produce a protective response without causing the actual disease. When a vaccine antigen enters the body:

The immune system recognizes it as foreign.
B lymphocytes produce specific antibodies.
T lymphocytes help coordinate the immune response.
Memory cells are formed for long-term protection.

This process enables a faster and stronger response upon future exposure to the real pathogen.

3. What are the different types of vaccines?

Vaccines are classified based on how the antigen is prepared to trigger immunity. The main types of vaccines include:

Live attenuated vaccines – contain weakened forms of the pathogen (e.g., measles vaccine).
Inactivated vaccines – contain killed pathogens (e.g., polio IPV).
Subunit or recombinant vaccines – contain specific antigenic parts of the pathogen (e.g., hepatitis B vaccine).
Toxoid vaccines – contain inactivated toxins (e.g., tetanus vaccine).
mRNA vaccines – use messenger RNA to instruct cells to produce a viral protein (e.g., some COVID-19 vaccines).

Each type safely stimulates an immune response.

4. What is the difference between active and passive immunisation?

Active immunisation involves the body producing its own antibodies, while passive immunisation involves receiving ready-made antibodies. In active immunisation:

Antigens stimulate the immune system.
Memory cells are formed.
Protection is long-lasting.

In passive immunisation:

Preformed antibodies are given (e.g., antivenom).
No memory cells are formed.
Protection is immediate but temporary.

5. Why are booster doses needed in vaccination?

Booster doses are needed to reinforce and prolong the immune response generated by the initial vaccination. Over time, the level of antibodies may decline. A booster dose:

Re-exposes the immune system to the antigen.
Stimulates rapid activation of memory cells.
Increases antibody concentration to protective levels.

This ensures long-term immunity against the disease.

6. What is herd immunity in immunisation?

Herd immunity is the indirect protection from infectious disease that occurs when a large proportion of a population becomes immune. When enough individuals are immunised through vaccination:

The spread of the pathogen is reduced.
Transmission chains are interrupted.
Non-immunised individuals receive indirect protection.

The required percentage for herd immunity depends on the disease’s contagiousness.

7. What is an antigen in vaccination?

An antigen in vaccination is a substance that triggers an immune response and antibody production. In vaccines, the antigen may be:

A weakened or killed pathogen.
A fragment of a pathogen, such as a protein.
An inactivated toxin (toxoid).

The antigen is recognized as foreign by the immune system, leading to the formation of specific antibodies and memory cells.

8. Can vaccines cause the disease they are meant to prevent?

Most vaccines cannot cause the disease because they contain weakened, inactivated, or non-infectious components of the pathogen. Inactivated and subunit vaccines do not contain live pathogens, so they cannot replicate. Live attenuated vaccines use weakened organisms that are unlikely to cause disease in healthy individuals. Mild symptoms like fever may occur, but these are signs of immune activation, not the actual disease.

9. How does immunological memory develop after vaccination?

Immunological memory develops when exposure to a vaccine antigen leads to the formation of long-lived memory cells. During the primary immune response:

B cells differentiate into plasma cells that produce antibodies.
Some B and T cells become memory cells.

Upon re-exposure, the secondary immune response is faster and stronger, providing effective protection against the pathogen.

10. Why is vaccination important for public health?

Vaccination is important for public health because it prevents infectious diseases and reduces their spread in communities. Through widespread immunisation: