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The science behind how vaccines work

Ever since the world entered the ‘pandemic era’ in March 2020, the Coronavirus has claimed more than 3 million lives and the numbers are surging every moment. With the virus having upended the lives of people across the globe, countries have been struggling to combat its spread.



Fortunately, COVID-19 vaccination is now offering a way to return to the normalcy of life we all hope for. The beginning of 2021 saw numerous vaccines being given emergency approval, which are now being available to the masses. However, there has also been much concern and skepticism regarding the Covid-19 vaccination.


The apprehension stems from a lack of information about how vaccines work. To understand how the human body responds to vaccines, it is important to be acquainted with the functioning of the human immune system.


The Immune System Many diseases are caused by foreign organisms (Pathogens) entering our bodies- bacteria, viruses, parasites, fungi. Pathogens once they enter our bodies tend to reproduce and multiply, leading to infection and potential illnesses. To combat the spread, our bodies respond with a natural defense mechanism, or what we normally call the immune system.


The subpart of a pathogen that causes the formation of antibodies is called an antigen. When the human body is exposed to an antigen for the first time, it takes time for the immune system to respond and produce antibodies specific to that antigen. This is exactly when the person is susceptible to catching an illness.

The antigen-specific antibodies, once developed in our bodies, work with the rest of the immune system to destroy the pathogen and stop the disease. These antibodies also have memory cells, which means that if the body is exposed to the same pathogen ever again, the memory cells will ensure to attack the foreign organisms and respond much faster to protect against the illness.


What is a vaccine? A vaccine is a type of medicine that trains the body’s immune system so that it can fight a disease it has not come into contact with before. A vaccine contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as a threat and to produce antibodies to destroy the threat.

When the microbes infect the body in the future, there is a stronger and quicker response by the immune system to produce antibodies against it due to what is known as immunological memory or the ability of the immune system to respond more rapidly and effectively to a previously encountered pathogen. This provides immunity against the disease.


Vaccines and herd immunity When a large number of people are protected from a disease by vaccination, the spread of the pandemic reduces drastically. Vaccination ensures that a person becomes resistant to the virus and with enough people becoming resistant; it becomes difficult for the virus to enter the human body. It is also well known that viruses cannot survive outside for long. Hence, vaccination of a large number of the population also ensures the safety of those who have not been vaccinated yet.


Having said that, no vaccine can provide complete protection and neither can herd immunity ensure complete safety for all. However, it can reduce the transmission drastically.

As the global death toll for Covid-19 continues to rise, vaccines emerge as the most important solution to curb the spread and transition to normalcy.