How does a vaccine work? Will it help you fight?

Our immune system works in various ways to tackle the organisms that enter our body. These organisms can damage all other systems. Any individual can be susceptible to infection. So, one needs to train the immune system to fight off the infection. A vaccine is the only solution. But the important question is, ‘how does a vaccine work?’ A

A vaccine is given to an individual in one or many doses at any age, depending on the disease. It is not any kind of drug administered into the system; instead, it is the causative organism of the disease. Before administration, they attenuate or kill the organism. DNA based vaccines and conjugate vaccines are a better choice and thus are under development.


  • Immune system: The groups of cells and tissues working together to treat a disease
  • Organism: Any biotic species like bacteria or virus
  • Pathogen: Any organism with the ability to cause a disease
  • Infection: Infection is when a pathogen enters the host system
  • Disease: When the infection causes a specific malfunction
  • Host: The living body on which another organism depends for nutrition
  • Antigen: Any specific bio-molecule capable of triggering an immune response
  • Antibody: Proteinaceous structures produced by the host to tackle the foreign antigen
  • Immunogenicity: The capacity of the antigen to elicit an immune response
  • Pathogenicity/virulence: The ability of an antigen to cause the malfunction
  • Immune response: The host activity in response to the antigen (includes fever, inflammation)

The action of the immune system

When the organism enters the system via a vaccine, the immune cells recognize it as an antigen (foreign body) and start attacking it. An antigen can be any protein of the specific organism capable of triggering an immune response. In this process, a group of cells – white blood cells act like soldiers. It comprises the macrophages, B lymphocytes, and T lymphocytes.


Macrophages are the primary army of the system. They work based on apoptosis, i.e., programmed cell death. With chemical signals, they gradually move towards an antigen, and by the process of endocytosis, they engulf it. The lysozyme present within the macrophage degrades the antigen.

B lymphocytes

They are also called B-cells. They are abundantly present in the bone marrow and mature in the same. During maturation (after encountering antigen presented with MHC), they differentiate into memory B cells and cytotoxic B-cells (plasma cells). The plasma cells produce antibodies to tackle the antigen. Whereas, the memory B cells, remember the structure of the antigen for a quicker response next time. They are the significant components of humoral immunity.

T lymphocytes

They are also called T-cells. They are abundantly present in the Thymus, where they undergo maturation (after encountering antigen presented with MHC) as well. T-cells also differentiate into cytotoxic and memory T-cells. The T4 cells or the T-helper cells primarily recognize an antigen and trigger an immune response by activating the B-cells. Hence, they are significant components of cell-mediated immunity.

These WBCs have receptors on the surface capable of adhering to the antigen for its activity. There is a rise in temperature during this period. Hence the first sign of identification is fever.

How does a vaccine work in the immune system?

In this era of dangerous infections by bacteria and viruses, it is essential to train our body to kill it before it kills us. A vaccine trains the system for the same.

When a dead organism enters the body in the form of a vaccine, the immune system activates to tackle the organism. A crucial point to note here is-the organism is either killed or attenuated so that it can only trigger an immune response and cannot cause the disease.

The memory system remembers the structure of the antigen. In this process, the antibodies entirely degrade the organism and are still abundantly present, all ready to kill the microbe, the very next moment it enters the system.

Under a typical infection, the memory cells recognize it as the same antigen encountered previously; and wake up the other cells of the system to kill the organism before it starts attacking the body. A vaccinated individual remains unaffected during the course of infection.

Is natural immunity better or a vaccine?

Although natural immunity is better than a vaccine, it is essential to note that the former is risky. In the event of an infection, if the system is not docile to tackle the organism, it can take a long time to develop antibodies against it. During this course, the body is wholly compromised, giving the microbe the total control.

Administration based on how a vaccine works

There are various vaccines developed to counteract the microbial infection. The first one ever to develop was for smallpox by Edward Jenner, followed by Cholera, Rabies, Hepatitis, Tuberculosis, Polio, and many more.

  • Dead: It includes heat or chemical treatment to kill a specific bacteria or virus. They then introduce these dead cells into the body. Heat killed vaccines may pose some problems as it requires more than one dose for efficiency. Example: Polio, Hepatitis A, and Rabies.
  • Live Attenuated: It refers to the asymptomatic form of an organism. In this process, it is not entirely killed; rather, it loses its virulence (ability to cause the disease). All the other proteins act as antigens and trigger an immune response. Example: Measles, Mumps, and Rubella.

The incomplete inactivation of these organisms can sometimes revert to its pathogenic form, causing an infection. Genetic manipulation or genetically engineered vaccines would be a better choice and has fewer side effects over conventional vaccines.

  • DNA-based vaccines: DNA vaccines include the introduction of pathogen’s DNA after dispensing all the other parts of the bacteria or virus. This DNA is capable of eliciting an immune response training the system beforehand.
  • Vector vaccines: A vector is something that helps with transport. These are similar to DNA vaccines, but the only difference is that these vaccines use a weak bacterium or virus as a vehicle to transfer the immunogenic DNA into the system.

Why is it challenging to develop a vaccine for viruses such as Ebola and HIV?

A very rapid mutation rate would be the answer to this challenging task. For instance, viruses like HIV, Ebola, and Influenza have a rapid mutation rate making it difficult to develop a vaccine. On the other hand, it is essential to grow the organism in-vitro under an artificially controlled environment, to develop a vaccine. Viruses being obligate parasites, require a living cell for its growth. Hence, it is not easy to create a vaccine by altering the activity of a virus as it is for a bacterium.

Can the work of a vaccine affect us?

The side effects of a vaccine are that they cause mild fever and inflammatory responses like redness or a rash at the site of administration. People misread these signs, and a few occurrences of the specific disease right after a vaccine convinced them that the activity of the vaccine itself causes the disease.

It typically takes some time for the immune system to train itself against the organism. If the individual encounters the illness after a few days of vaccination, it’s because the system is not ready to fight off the infection.

A very well-known side effect of a vaccine is exposure to Mercury. Parents refuse to vaccinate their kids due to the fear of mercury exposure. An essential chemical, Thimerosal, present in vaccines consists of Mercury. It is necessary for preservation. It inhibits the growth of undesirable bacteria because receiving a vaccine with contaminated bacteria can be deadly.

Reputable scientific studies have shown that Thimerosal can cause autism. Some examined the rates of autism in a state or a country. But, the rates didn’t go down even after they removed Thimerosal from the vaccine, finally concluding no relation between a vaccine and autism.

What happens if you don’t get vaccinated?

It is always better to safeguard yourself and your kids against a specific disease rather than treating it after its occurrence. If a large number of individuals in a community or society undergo the vaccination against a particular illness, it leads to herd immunity. Herd immunity is when a large number prevents the occurrence of the disease, it gradually reduces the pathogen’s prevalence in the community. It decreases the proportion of infected individuals.

Unfortunately, few people are not fit for a vaccine. There are different age factors and health complications that crowd the judgment.

Related: How to increase immunity with diet?

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